Electrode body, thin-film el device comprising the same, method for manufacturing the same, and display and illuminator comprising the thin-film el device

ABSTRACT

A thin film EL device is disclosed which includes a hole-injecting electrode, an electron-injecting electrode paired with the hole-injecting electrode, and a functional layer provided between the hole-injecting electrode and the electron-injecting electrode and emitting light by application of an electric field produced by the electrodes. The electron-injecting electrode contains at least two or more different metals having different work functions and a capturing substance for capturing a low work function metal, which is a metal other than a highest work function metal among the above-described metals, in its ionic state. This configuration prevents deterioration of the low work function metal, increasing the luminance and lifetime of the device.

TECHNICAL FIELD

[0001] The present invention relates to a thin film EL device applied tolighting such as a backlight for a light-emitting display and a liquidcrystal display and a method of fabricating such a thin film EL device.The present invention further relates to a display device and a lightingsystem provided with the thin film EL device.

BACKGROUND ART

[0002] Thin film EL devices provided with electroluminescent(hereinafter referred to as EL) panels have features such as highvisibility, excellent display capability, and high speed response.

[0003] Of the thin film EL devices, on, for example, organic EL devicesutilizing organic compounds as the constituent material, various reportshave been made. Among these reports, for example, C. W. Tang et al.proposed an organic electroluminescent device (organic EL device) havingan organic luminescent layer and a hole-transporting layer stacked ontop of each other (Applied Physics Letters, 51, 1987, p. 913). Up untiltoday, the research and development of the thin film EL device have beenconducted based on this organic electroluminescent device having a basicconfiguration.

[0004] The basic configuration of the organic electroluminescent devicewill be described below.

[0005]FIG. 16 is a schematic cross-sectional view showing a prior artorganic electroluminescent device. The organic electroluminescent devicehas, as shown in the figure, a transparent electrode 102, ahole-transport layer 103, an electron-transporting luminescent layer104, and a cathode 105 stacked in sequence on a glass substrate 101. Inanother configuration, the electron-transporting luminescent layer 105may be divided by functions into an electron-transport layer and aluminescent layer.

[0006] It should be noted that the thin film EL device is defined as adevice in which functional layers interposed between the transparentelectrode 102 and the cathode 105 are organic layers, inorganic layers,or mixed layers of an organic layer and an inorganic layer. The organicelectroluminescent device is defined as a device in which the functionallayers interposed between the transparent electrode 102 and the cathode105 are organic layers.

[0007] Here, the cathode 105 utilizes an alloy composed of an alkalimetal or an alkaline earth metal which has a low work function and astable metal such as aluminum or silver, as the cathode with which,electron injection is performed stably and readily. Specific example ofthe cathode 105 made of the alloy is disclosed, for example, in JapaneseUnexamined Patent Publication No. 5-121172. In this publication, it isdescribed that an alloy composed of aluminum and lithium is utilized andthe Li concentration is controlled in the trace range from 0.01 wt % to0.1 wt %. Thereby, an organic electroluminescent device with highelectroluminescent efficiency and high environmental stability can berealized.

[0008] In relation to the prior art described in the above-describedpublication, another organic EL device is disclosed which has, in placeof the cathode 105, a metal thin film serving as an electron-injectingelectrode and an electrode film serving as a passivating electrodestacked in sequence on the organic layer. The metal thin film iscomposed of a low work function metal material such as an alkali metalor an alkaline earth metal, and the electrode film is composed of ametal material which is stable to oxygen and water. With such aconfiguration, the electrode film can protect the metal thin film, whichhas a high reactivity with moisture and the like, from the outside,thereby maintaining electron injection efficiency. Furthermore, since itis not necessary to control Li and the like at low concentrations,device fabrication with simplified processes is made possible.

[0009] Moreover, in recent years, an organic electroluminescent devicehaving, as shown in FIG. 17, an electron-injecting layer 106 providedbetween an electron-transporting luminescent layer 104 and a cathode 105has been disclosed (Japanese Unexamined Patent Publication No. 9-17574).In this publication, it is disclosed that the electron-injecting layer106 utilizes an alkali metal compound as the material, and by optimizingthe film thickness of the electron-injecting layer 106, light emissionwith high luminance can be obtained. Furthermore, it is described thatbecause alkali metal compounds are chemically stable, reproducibility ofcharacteristics is high, making it possible to obtain an organic ELdevice capable of emitting light with high luminance at low appliedvoltages.

[0010] As for an electron-injecting layer composed of an insulatingsubstance, the relationship between the film thickness and a dark spot(a region where there is no light emission) and the like are reported indetail (T. Wakimoto, Y Fukuda, K. Nagayama, A Yokoi, H. Nakada, and M.Tsuchida, IEEE Transactions on Electron Devices, Vol. 44, No. 8, p.1245, 1997).

[0011] The present inventors have developed an organicelectroluminescent device which utilizes, as the material for theelectron-injecting layer, a specific organic metal complex compoundcontaining an alkali metal or an alkaline earth metal as the centralmetal, or an electron-deficient compound. With an organicelectroluminescent device having the electron-injecting layer utilizingsuch materials, an electroluminescent device with high luminance andlong lifetime can be obtained without the need to use low work functionmetal materials.

[0012] As has been described, in developing the organicelectroluminescent device, the electron-injecting layer is a key elementin determining electroluminescent efficiencies and lifetimes. From thisperspective, various improvements have been made.

[0013] When these organic electroluminescent devices are driven underduty drive conditions, for practical application, the instantaneousluminance reaches several thousands to several ten-thousands of cd/m².Thus, when driving the organic electroluminescent device, it isnecessary to maintain high efficiencies even in such a high luminanceregion. Hence, in prior art organic electroluminescent devices, theluminance needs to be further increased. To realize this, it isindispensable to use an electrode containing an alkali metal or analkaline earth metal which has an excellent electron injectionefficiency.

[0014] The electrode utilizing such a low work function metal material,however, may cause degradation in device characteristics due todeterioration of the metal. In order to prevent the degradation, as isdescribed above, a method employing a configuration in which low workfunction metal compounds are utilized was attempted. With this method,when utilizing inorganic metal compounds, satisfactory improvement wasnot made in terms of efficiencies and lifetimes. On the other hand, whenutilizing organic metal compounds, although some improvement was made interms of degradation of device characteristics, for achieving furtherimprovement, simple metals with low work function were required to beutilized as the electrode material.

[0015] Thus, when low work function simple metals with high reactivityare utilized as the electrode material, deterioration of the simplemetals must be prevented.

DISCLOSURE OF THE INVENTION

[0016] In view of the foregoing and other problems, it is an object ofthe present invention to increase, for practical applications, theluminance and lifetime of a thin film EL device, in which a low workfunction metal with excellent electron injection efficiency is containedin, for example, an electron-injecting electrode, by preventingdeterioration of the low work function metal.

[0017] The present inventors have investigated the determining factorfor the lifetime characteristics of the thin film EL device and thenemployed the configuration which inhibits the mechanism of the factor.Thereby, the thin film EL device realized a long lifetime whilemaintaining light emission with high luminance and high reproducibility.In addition, the present inventors have discovered fabrication methodsby which thin film EL devices with excellent characteristics can beconstantly fabricated, and at the same time high-grade display devicesand lighting systems can be provided.

[0018] (Electrodes)

[0019] (1) According to a first aspect of the present invention, thereis provided an electrode comprising: at least two or more differentmetals having different work functions; and an electron-deficientsubstance for accepting electrons emitted from a low work functionmetal, the low work function metal being a metal other than a highestwork function metal among the metals.

[0020] With the above-described configuration, because anelectron-deficient substance is a strong Lewis acid, the substancecaptures electrons and becomes an anion. This anion can satisfy theoctet rule by accepting electrons, and thus a forward reaction is morelikely to occur. As a result, the substance can exist stably in theelectrode in its anionic state, making it possible to obtain anelectrode with excellent electron injection efficiency.

[0021] The above-described configuration may further comprise: anelectron-deficient substance layer containing the electron-deficientsubstance; and a metal layer provided on the electron-deficientsubstance layer and containing an alloy composed of the two or moredifferent metals

[0022] In addition, the above-described configuration may furthercomprise: an electron-deficient substance layer containing theelectron-deficient substance; a low work function metal layer providedon the electron-deficient substance layer and containing the low workfunction metal; and a passivating metal layer provided on the low workfunction metal layer and containing the highest work function metal.

[0023] The above-described configuration may further comprise: a lowwork function metal layer containing the electron-deficient substanceand the low work function metal; and a passivating metal layer providedon the low work function metal layer and containing the highest workfunction metal.

[0024] Furthermore, the above-described configuration may be such thatan alloy composed of the at least two or more different metals havingdifferent work functions and the electron-deficient substance arecontained in a same layer.

[0025] The electron-deficient substance in each of the above-describedconfiguration may be a compound represented by the following chemicalformula (1):

[0026] where R¹ and R² each independently is one selected from the groupconsisting of a bridging ligand containing a nitrogen-containingaromatic ring, a bridging ligand containing a derivative of anitrogen-containing aromatic ring, halogen, and a bridging ligandcontaining alkyl of 1 to 3 carbons, the nitrogen-containing aromaticring and the derivative of the nitrogen-containing aromatic ring eachhaving at least one nitrogen atom as coordinating atom; R³, R⁴, R⁵, andR⁶ each independently is one selected from the group consisting ofhydrogen, alkyl, an aryl derivative, and a derivative of anitrogen-containing aromatic ring having one nitrogen atom ascoordinating atom; and M¹ is a central metal.

[0027] (2) According to a second aspect of the present invention, thereis provided an electrode comprising: at least two or more differentmetals having different work functions; and a capturing substance forcapturing a low work function metal in its ionic state, the low workfunction metal being a metal other than a highest work function metalamong the metals.

[0028] When a low work function metal emits electrons and becomes acation, the cation attempts to fill electrons in the outer shell orbitalhaving lost its valence electrons, which in turn provides a strongoxidizing action to the cation. A capturing substance captures such alow work function metal in its ionic state, and thus it is possible toprevent the low work function metal from becoming an insulator such asan oxide, resulting from reaction with water and the like. Consequently,the lifetime of the electrode can be increased.

[0029] The above-described configuration may further comprise: a lowwork function metal layer provided on the capture layer and containingthe low work function metal; and a passivating metal layer provided onthe low work function metal layer and containing the highest workfunction metal.

[0030] Furthermore, the above-described configuration may furthercomprise: a capture layer containing the capturing substance; and ametal layer provided on the capture layer and containing an alloycomposed of the two or more different metals.

[0031] The above-described configuration may further comprise: a lowwork function metal layer containing the capturing substance and the lowwork function metal; and a passivating metal layer provided on the lowwork function metal layer and containing the highest work functionmetal.

[0032] (3) According to a third aspect of the present invention, thereis provided an electrode comprising: at least two or more differentmetals having different work functions; a capturing substance forcapturing a low work function metal in its ionic state, the low workfunction metal being a metal other than a highest work function metalamong the metals; and an electron-deficient substance for acceptingelectrons emitted from the low work function metal.

[0033] With the above-described configuration, since the electrodecontains a capturing substance as well as an electron-deficientsubstance, excellent electron injection efficiency can be achieved andthe lifetime can be increased.

[0034] The above-described configuration may further comprise: anelectron-deficient substance layer containing the electron-deficientsubstance; a capture layer contacting the electron-deficient substancelayer and containing the capturing substance; a low work function metallayer contacting the electron-deficient substance layer or the capturelayer and containing the low work function metal; and a passivatingmetal layer contacting the low work function metal layer and containingthe highest work function metal.

[0035] In addition, the above-described configuration may furthercomprise: an electron-deficient substance layer containing theelectron-deficient substance; a low work function metal layer providedon the electron-deficient substance layer and containing the capturingsubstance and the low work function metal; and a passivating metal layerprovided on the low work function metal layer and containing the highestwork function metal.

[0036] (Thin Film EL Devices)

[0037] A thin film EL device according to the present invention canemploy Aspects (4) to (6), as will be described below. Aspects (1) to(3) respectively correspond to the first to the third aspects describedabove.

[0038] (4) A thin film EL device of the present invention correspondingto the first aspect may comprise: a hole-injecting electrode; anelectron-injecting electrode paired with the hole-injecting electrode;and a functional layer provided between the hole-injecting electrode andthe electron-injecting electrode and emitting light by application of anelectric field produced by the electrodes, wherein theelectron-injecting electrode contains at least two or more differentmetals having different work functions and an electron-deficientsubstance for accepting electrons emitted from a low work functionmetal, the low work function metal being a metal other than a highestwork function metal among the metals.

[0039] With the above-described configuration, since theelectron-injecting electrode contains an electron-deficient substancewith excellent electron transport efficiency, electrons can beefficiently injected into the functional layer. As a result, a thin filmEL device with high electroluminescent efficiency can be obtained.

[0040] The above-described configuration may be such that theelectron-injecting electrode includes: an electron-deficient substancelayer provided on the functional layer and containing theelectron-deficient substance; and a metal layer provided on theelectron-deficient substance layer and containing the at least two ormore different metals having different work functions.

[0041] Furthermore, the above-described configuration may be such thatthe electron-deficient substance layer contains the low work functionmetal.

[0042] Another thin film EL device of the present inventioncorresponding to the first aspect may comprise: an electron-injectingelectrode containing at least two or more different metals havingdifferent work functions; a hole-injecting electrode paired with theelectron-injecting electrode; and a functional layer provided betweenthe electron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein the functional layer contains at least on a side ofthe electron-injecting electrode an electron-deficient substance foraccepting electrons emitted from a low work function metal, the low workfunction metal being a metal other than a highest work function metalamong the metals.

[0043] With the above-described configuration, because anelectron-deficient substance is contained in the functional layer, it ispossible to improve the transport properties of electrons, within thefunctional layer, injected from the electron-injecting electrode.Thereby, electroluminescent efficiency can be improved.

[0044] The above-described configuration may be such that theelectron-deficient substance is uniformly contained on a side of theelectron-injecting electrode within a given area.

[0045] In addition, the above-described configuration may be such thatthe electron-deficient substance is contained in the functional layer ona side of the electron-injecting electrode within a given area and isdistributed such that a concentration thereof gradually increases towardthe electron-injecting electrode.

[0046] Still another thin film EL device of the present inventioncorresponding to the first aspect may comprise: an electron-injectingelectrode; a hole-injecting electrode paired with the electron-injectingelectrode; and a functional layer provided between theelectron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein the functional layer contains a low work functionmetal and an electron-deficient substance, the low work function metalhaving a lower work function than the electron-injecting electrode andthe electron-deficient substance accepting electrons emitted from thelow work function metal.

[0047] The above-described configuration may be such that theelectron-deficient substance is uniformly contained on a side of theelectron-injecting electrode within a given area.

[0048] The above-described configuration may be such that theelectron-deficient substance is contained in the functional layer on aside of the electron-injecting electrode within a given area and isdistributed such that a concentration thereof gradually increases towardthe electron-injecting electrode.

[0049] (5) A thin film EL device of the present invention correspondingto the second aspect may comprise: a hole-injecting electrode; anelectron-injecting electrode paired with the hole-injecting electrode;and a functional layer provided between the hole-injecting electrode andthe electron-injecting electrode and emitting light by application of anelectric field produced by the electrodes, wherein theelectron-injecting electrode contains at least two or more differentmetals having different work functions and a capturing substance forcapturing a low work function metal in its ionic state, the low workfunction metal being a metal other than a highest work function metalamong the metals.

[0050] With the above-described configuration, a capturing substancecaptures a low work function metal in its ionic state, therebyinhibiting the low work function metal from becoming an insulator.Consequently, the low work function metal can stably inject electronsover a long period of time. Thus, it is possible to obtain lightemission with high luminance and to provide a thin film EL device with along light-emission lifetime.

[0051] The above-described configuration may be such that theelectron-injecting electrode includes: a capture layer provided on thefunctional layer and containing the capturing substance; and a metallayer provided on the capture layer and containing the at least two ormore different metals having different work functions.

[0052] Furthermore, the above-described configuration may be such thatthe capture layer contains the low work function metal.

[0053] Another thin film EL device of the present inventioncorresponding to the second aspect may comprise: an electron-injectingelectrode containing at least two or more different metals havingdifferent work functions; a hole-injecting electrode paired with theelectron-injecting electrode; and a functional layer provided betweenthe electron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein the functional layer contains on a side of theelectron-injecting electrode a capturing substance for capturing a lowwork function metal in its ionic state, the low work function metalbeing a metal other than a highest work function metal among the metals.

[0054] As with the above-described configuration, in the case also wherea capturing substance is contained in the functional layer, it ispossible to inhibit a low work function metal from becoming aninsulator, by capturing the low work function metal in its ionic state.As a result, a thin film EL device with high luminance and long lifetimecan be provided.

[0055] The above-described configuration may be such that the capturingsubstance is uniformly contained on a side of the electron-injectingelectrode within a given area.

[0056] Furthermore, the above-described configuration may be such thatthe capturing substance is contained in the functional layer on a sideof the electron-injecting electrode within a given area and isdistributed such that a concentration thereof gradually increases towardthe electron-injecting electrode.

[0057] Still another thin film EL device of the present inventioncorresponding to the second aspect may comprise: an electron-injectingelectrode; a hole-injecting electrode paired with the electron-injectingelectrode; and a functional layer provided between theelectron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein the functional layer contains a low work functionmetal and a capturing substance for capturing the low work functionmetal in its ionic state, the low work function metal having a lowerwork function than the electron-injecting electrode.

[0058] The above-described configuration may be such that the low workfunction metal and the capturing substance are uniformly contained on aside of the electron-injecting electrode within a given area.

[0059] In addition, the above-described configuration may be such thatthe low work function metal and the capturing substance are contained inthe functional layer on a side of the electron-injecting electrodewithin a given area and are distributed such that concentrations thereofgradually increase toward the electron-injecting electrode.

[0060] (6) A thin film EL device of the present invention correspondingto the third aspect may comprise: a hole-injecting electrode; anelectron-injecting electrode paired with the hole-injecting electrode;and a functional layer provided between the hole-injecting electrode andthe electron-injecting electrode and emitting light by application of anelectric field produced by the electrodes, wherein theelectron-injecting electrode contains: at least two or more differentmetals having different work functions; an electron-deficient substancefor accepting electrons emitted from a low work function metal, the lowwork function metal being a metal other than a highest work functionmetal among the metals; and a capturing substance for capturing the lowwork function metal in its ionic state.

[0061] With the above-described configuration, since theelectron-injecting electrode contains an electron-deficient substance,the electron injection efficiency to the functional layer is excellent.Thus, electroluminescent efficiency can be improved. In addition, theelectron-injecting electrode also contains a capturing substance, andtherefore it is possible to prevent a low work function metal fromdeteriorating and becoming an insulator Hence, it becomes possible tocontinuously and stably inject electrons into the functional layer,increasing the lifetime of the device.

[0062] The above-described configuration may be such that theelectron-injecting electrode includes: an electron-deficient substancelayer containing the electron-deficient substance; a capture layercontacting the electron-deficient substance layer and containing thecapturing substance; and a metal layer containing the two or moredifferent metals.

[0063] The above-described configuration may be such that theelectron-injecting electrode includes: an electron-deficient substancelayer containing the electron-deficient substance; and a capture layercontacting the electron-deficient substance layer and containing thecapturing substance and the low work function metal.

[0064] Another thin film EL device of the present inventioncorresponding to the third aspect may comprise: an electron-injectingelectrode containing at least two or more different metals havingdifferent work functions; a hole-injecting electrode paired with theelectron-injecting electrode; and a functional layer provided betweenthe electron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein the functional layer contains an electron-deficientsubstance for accepting electrons emitted from a low work function metaland a capturing substance for capturing the low work function metal inits ionic state, the low work function metal being a metal other than ahighest work function metal among the metals.

[0065] As with the above-described configuration, in the case also wherean electron-deficient substance and a capturing substance are containedin the functional layer, it is possible to improve electroluminescentefficiency and increase the luminance and lifetime of the device.

[0066] The above-described configuration may be such that theelectron-deficient substance and the capturing substance are uniformlycontained on a side of the electron-injecting electrode within a givenarea.

[0067] The above-described configuration may be such that theelectron-deficient substance and the capturing substance are containedin the functional layer on a side of the electron-injecting electrodewithin a given area and are distributed such that concentrations thereofgradually increase toward the electron-injecting electrode.

[0068] Moreover, still another thin film EL device of the presentinvention corresponding to the third aspect may comprise: anelectron-injecting electrode; a hole-injecting electrode paired with theelectron-injecting electrode; and a functional layer provided betweenthe electron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein the functional layer contains a low work functionmetal having a lower work function than the electron-injectingelectrode, a capturing substance for capturing the low work functionmetal in its ionic state, and an electron-deficient substance foraccepting electrons emitted from the low work function metal

[0069] The above-described configuration may be such that the low workfunction metal, the electron-deficient substance, and the capturingsubstance are uniformly contained on a side of the electron-injectingelectrode within a given area.

[0070] In addition, the above-described configuration may be such thatthe low work function metal, the electron-deficient substance, and thecapturing substance are contained in the functional layer on a side ofthe electron-injecting electrode within a given area and are distributedsuch that concentrations thereof gradually increase toward theelectron-injecting electrode.

[0071] Furthermore, yet another thin film EL device of the presentinvention corresponding to the third aspect may comprise: anelectron-injecting electrode containing at least two or more differentmetals having different work functions; a hole-injecting electrodepaired with the electron-injecting electrode; and a functional layerprovided between the electron-injecting electrode and the hole-injectingelectrode and emitting light by application of an electric fieldproduced by the electrodes, wherein one of an electron-deficientsubstance for accepting electrons emitted from a low work function metaland a capturing substance for capturing the low work function metal inits ionic state is contained in the electron-injecting electrode and theother is contained in the functional layer, the low work function metalbeing a metal other than a highest work function metal among the metals

[0072] (Methods of Fabricating Thin Film EL Devices)

[0073] As the methods of fabricating the above-described thin film ELdevices, Aspects (7) to (9), as will be described below, can beemployed. Aspects (7) to (9) respectively correspond to Aspects (4) to(6) described above.

[0074] (7) A method of fabricating a thin film EL device of the presentinvention corresponding to the first aspect is a method of fabricating athin film EL device having an electron-injecting electrode containing atleast two or more different metals having different work functions, ahole-injecting electrode, and a functional layer provided between theelectrodes for emitting light by application of an electric fieldproduced by the electrodes, and the method may comprise: forming theelectron-injecting electrode, the forming of the electron-injectingelectrode comprising at least: forming on a side of the functional layeran electron-deficient substance layer containing an electron-deficientsubstance for accepting electrons emitted from a low work functionmetal, the low work function metal being a metal other than a highestwork function metal among the metals; and forming on an opposite sidefrom the functional layer a metal layer containing the two or moredifferent metals.

[0075] Another method of fabricating a thin film EL device of thepresent invention corresponding to the first aspect is a method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe electron-injecting electrode, the forming of the electron-injectingelectrode comprising at least: forming on a side of the functional layeran electron-deficient substance layer containing a low work functionmetal and an electron-deficient substance for accepting electronsemitted from the low work function metal, the low work function metalbeing a metal other than a highest work function metal among the metals.

[0076] Still another method of fabricating a thin film EL device of thepresent invention corresponding to the first aspect is a method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe functional layer so that an electron-deficient substance isdistributed in the functional layer at least on a side of theelectron-injecting electrode, the electron-deficient substance acceptingelectrons emitted from a low work function metal, the low work functionmeal being a metal other than a highest work function metal among themetals.

[0077] Yet another method of fabricating a thin film EL device of thepresent invention corresponding to the first aspect is a method offabricating a thin film EL device having an electron-injectingelectrode, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe functional layer so that a low work function metal and anelectron-deficient substance are distributed in the functional layer atleast on a side of the electron-injecting electrode, the low workfunction metal being a metal other than a highest work function metalamong the metals and the electron-deficient substance acceptingelectrons emitted from the low work function metal.

[0078] With the above-described methods, deterioration of a low workfunction metal can be prevented, and thus it is possible to fabricate athin film EL device with high light-emission luminance. In addition,when the electron-injecting electrode is formed, for example, from anelectron-deficient substance layer and a metal layer containing a lowwork function metal, the film thickness of the metal layer can be madeeven thinner, improving workability. Further, variations inlight-emission luminance in the plane can be controlled, and thus it ispossible to fabricate a device with good reproducibility and to enhancereliability of the fabrication process. Yield can also be improved.

[0079] (8) A method of fabricating a thin film EL device of the presentinvention corresponding to the second aspect is a method of fabricatinga thin film EL device having an electron-injecting electrode containingat least two or more different metals having different work functions, ahole-injecting electrode, and a functional layer provided between theelectrodes for emitting light by application of an electric fieldproduced by the electrodes, and the method may comprise: forming theelectron-injecting electrode, the forming of the electron-injectingelectrode comprising at least: forming on a side of the functional layera capture layer containing a capturing substance for capturing a lowwork function metal in its ionic state, the low work function metalbeing a metal other than a highest work function metal among the metals;and forming a metal layer on an opposite side from the functional layer,the metal layer containing an alloy composed of the two or moredifferent metals.

[0080] Another method of fabricating a thin film EL device of thepresent invention corresponding to the second aspect is a method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe electron-injecting electrode, the forming of the electron-injectingelectrode comprising at least: forming on a side of the functional layera capture layer containing a capturing substance for capturing a lowwork function metal in its ionic state, the low work function metalbeing a metal other than a highest work function metal among the metals.

[0081] Still another method of fabricating a thin film EL device of thepresent invention corresponding to the second aspect is a method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe functional layer so that a capturing substance is distributed in thefunctional layer at least on a side of the electron-injecting electrode,the capturing substance capturing a low work function metal in its ionicstate, the low work function metal being a metal other than a highestwork function metal among the metals.

[0082] Yet another method of fabricating a thin film EL device of thepresent invention corresponding to the second aspect is a method offabricating a thin film EL device having an electron-injectingelectrode, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe functional layer so that a low work function metal and a capturingsubstance are distributed in the functional layer at least on a side ofthe electron-injecting electrode, the low work function metal being ametal other than a highest work function metal among the metals and thecapturing substance capturing the low work function metal in its ionicstate.

[0083] With the above-described methods, because a capturing substancecaptures a low work function metal having become a cation during thefabrication process, deterioration of the low work function metal can beinhibited. Consequently, it is possible to fabricate a thin film ELdevice with high light-emission luminance. In addition, when theelectron-injecting electrode is formed, for example, from a capturelayer and a metal layer containing a low work function metal, the filmthickness of the metal layer can be made even thinner. Thereby,workability can be improved. In addition, variations in light-emissionluminance in the plane can be controlled, and thus it is possible tofabricate a device with good reproducibility and to enhance reliabilityof the fabrication process. Further, yield can be improved.

[0084] (9) A method of fabricating a thin film EL device of the presentinvention corresponding to the third aspect is a method of fabricating athin film EL device having an electron-injecting electrode containing atleast two or more different metals having different work functions, ahole-injecting electrode, and a functional layer provided between theelectrodes for emitting light by application of an electric fieldproduced by the electrodes, and the method may comprise: forming theelectron-injecting electrode, the forming of the electron-injectingelectrode comprising at least: forming an electron-deficient substancelayer containing an electron-deficient substance for accepting electronsemitted from a low work function metal, the low work function metalbeing a metal other than a highest work function metal among the metals;forming a capture layer containing a capturing substance for capturingthe low work function metal in its ionic state; and forming a metallayer on the electron-deficient substance layer or the capture layer,the metal layer containing the two or more different metals.

[0085] Another method of fabricating a thin film EL device of thepresent invention corresponding to the third aspect is a method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe electron-injecting electrode, the forming of the electron-injectingelectrode comprising at least: forming a layer containing a low workfunction metal, an electron-deficient substance, and a capturingsubstance, the low work function metal being a metal other than ahighest work function metal among the metals, the electron-deficientsubstance accepting electrons emitted from the low work function metal,and the capturing substance capturing the low work function metal in itsionic state.

[0086] Still another method of fabricating a thin film EL device of thepresent invention corresponding to the third aspect is a method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe electron-injecting electrode, the forming of the electron-injectingelectrode comprising at least: forming an electron-deficient substancelayer containing an electron-deficient substance for accepting electronsemitted from a low work function metal, the low work function metalbeing a metal other than a highest work function metal among the metals;and forming a capture layer containing the low work function metal and acapturing substance for capturing the low work function metal in itsionic state.

[0087] Yet another method of fabricating a thin film EL device of thepresent invention corresponding to the third aspect is a method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe functional layer so that an electron-deficient substance foraccepting electrons emitted from a low work function metal and acapturing substance for capturing the low work function metal in itsionic state are distributed in the functional layer at least on a sideof the electron-injecting electrode, the low work function metal being ametal other than a highest work function metal among the metals.

[0088] Furthermore, another method of fabricating a thin film EL deviceof the present invention corresponding to the third aspect is a methodof fabricating a thin film EL device having an electron-injectingelectrode, a hole-injecting electrode, and a functional layer providedbetween the electrodes for emitting light by application of an electricfield produced by the electrodes, and the method may comprise: formingthe functional layer so that a low work function metal, anelectron-deficient substance, and a capturing substance are distributedin the functional layer at least on a side of the electron-injectingelectrode, the low work function metal being a metal other than ahighest work function metal among the metals, the electron-deficientsubstance accepting electrons emitted from the low work function metal,and the capturing substance capturing the low work function metal in itsionic state.

[0089] With the above-described methods, because an electron-deficientsubstance and a capturing substance prevent deterioration of a low workfunction metal, a thin film EL device with high light-emission luminancecan be fabricated. In addition, improved workability and goodreproducibility are achieved, thereby further enhancing reliability ofthe fabrication process. Moreover, yield can be improved.

[0090] A display device according to the present invention can employAspects (10) to (12), as will be described below. Aspects (10) to (12)respectively correspond to the first to the third aspects describedabove.

[0091] (10) A display device of the present invention corresponding tothe first aspect may comprise: an electron-injecting electrodecontaining at least two or more different metals having different workfunctions; a hole-injecting electrode paired with the electron-injectingelectrode; and a functional layer provided between theelectron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein the electron-injecting electrode contains anelectron-deficient substance for accepting electrons emitted from a lowwork function metal, the low work function metal being a metal otherthan a highest work function metal among the metals.

[0092] Another display device of the present invention corresponding tothe first aspect may comprise: a hole-injecting electrode; anelectron-injecting electrode paired with the hole-injecting electrode;and a functional layer provided between the hole-injecting electrode andthe electron-injecting electrode and emitting light by application of anelectric field produced by the electrodes, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains an electron-deficient substance for accepting electrons emittedfrom the low work function metal.

[0093] (11) A display device of the present invention corresponding tothe second aspect may comprise: an electron-injecting electrodecontaining at least two or more different metals having different workfunctions; a hole-injecting electrode paired with the electron-injectingelectrode; a functional layer provided between the electron-injectingelectrode and the hole-injecting electrode and emitting light byapplication of an electric field produced by the electrodes, wherein theelectron-injecting electrode contains a capturing substance forcapturing a low work function metal in its ionic state, the low workfunction metal being a metal other than a highest work function metalamong the metals.

[0094] Another display device of the present invention corresponding tothe second aspect may comprise: a hole-injecting electrode; anelectron-injecting electrode paired with the hole-injecting electrode; afunctional layer provided between the hole-injecting electrode and theelectron-injecting electrode and emitting light by application of anelectric field produced by the electrodes, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains a capturing substance for capturing the low work function metalin its ionic state.

[0095] (12) A display device of the present invention corresponding tothe third aspect may comprise: an electron-injecting electrodecontaining at least two or more different metals having different workfunctions; a hole-injecting electrode paired with the electron-injectingelectrode; and a functional layer provided between theelectron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein the electron-injecting electrode contains: anelectron-deficient substance for accepting electrons emitted from a lowwork function metal, the low work function metal being a metal otherthan a highest work function metal among the metals; and a capturingsubstance for capturing the low work function metal in its ionic state.

[0096] Another display device of the present invention corresponding tothe third aspect may comprise: a hole-injecting electrode; anelectron-injecting electrode paired with the hole-injecting electrode;and a functional layer provided between the hole-injecting electrode andthe electron-injecting electrode and emitting light by application of anelectric field produced by the electrodes, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains an electron-deficient substance for accepting electrons emittedfrom a low work function metal and a capturing substance for capturingthe low work function metal in its ionic state, the low work functionmetal being a metal other than a highest work function metal among themetals.

[0097] Still another display device of the present inventioncorresponding to the third aspect may comprise: an electron-injectingelectrode containing at least two or more different metals havingdifferent work functions; a hole-injecting electrode paired with theelectron-injecting electrode; and a functional layer provided betweenthe electron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein one of a capturing substance for capturing a lowwork function metal in its ionic state and an electron-deficientsubstance for accepting electrons emitted from the low work functionmetal is contained in the electron-injecting electrode and the other iscontained in the functional layer, the low work function metal being ametal other than a highest work function metal among the metals.

[0098] With the above-described configurations, by employing a thin filmEL device with high electroluminescent efficiency and high reliability,a high-grade display device can be provided. In addition, even when, forexample, the device is driven under duty drive conditions, a high-gradeimage display can be realized and a reduction in lifetime can beinhibited over a long period of time, ensuring high reliability.

[0099] A lighting system according to the present invention can employAspects (13) to (15), as will be described below. Aspects (13) to (15)respectively correspond to the first to the third aspects describedabove.

[0100] (13) A lighting system of the present invention corresponding tothe first aspect may comprise: an electron-injecting electrodecontaining at least two or more different metals having different workfunctions; a hole-injecting electrode paired with the electron-injectingelectrode; a functional layer provided between the electron-injectingelectrode and the hole-injecting electrode and emitting light byapplication of an electric field produced by the electrodes, wherein theelectron-injecting electrode contains an electron-deficient substancefor accepting electrons emitted from a low work function metal, the lowwork function metal being a metal other than a highest work functionmetal among the metals.

[0101] Another lighting system of the present invention corresponding tothe first aspect may comprise: a hole-injecting electrode; anelectron-injecting electrode paired with the hole-injecting electrode;and a functional layer provided between the hole-injecting electrode andthe electron-injecting electrode and emitting light by application of anelectric field produced by the electrodes, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains an electron-deficient substance for accepting electrons emittedfrom the low work function metal.

[0102] (14) A lighting system of the present invention corresponding tothe second aspect may comprise: an electron-injecting electrodecontaining at least two or more different metals having different workfunctions; a hole-injecting electrode paired with the electron-injectingelectrode; a functional layer provided between the electron-injectingelectrode and the hole-injecting electrode and emitting light byapplication of an electric field produced by the electrodes, wherein theelectron-injecting electrode contains a capturing substance forcapturing a low work function metal in its ionic state, the low workfunction metal being a metal other than a highest work function metalamong the metals.

[0103] Another lighting system of the present invention corresponding tothe second aspect may comprise: a hole-injecting electrode; anelectron-injecting electrode paired with the hole-injecting electrode;and a functional layer provided between the hole-injecting electrode andthe electron-injecting electrode and emitting light by application of anelectric field produced by the electrodes, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains a capturing substance for capturing the low work function metalin its ionic state.

[0104] (15) A lighting system of the present invention corresponding tothe third aspect may comprise: an electron-injecting electrodecontaining at least two or more different metals having different workfunctions; a hole-injecting electrode paired with the electron-injectingelectrode; and a functional layer provided between theelectron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein the electron-injecting electrode contains: anelectron-deficient substance for accepting electrons emitted from a lowwork function metal, the low work function metal being a metal otherthan a highest work function metal among the metals; and a capturingsubstance for capturing the low work function metal in its ionic state.

[0105] Another lighting system of the present invention corresponding tothe third aspect may comprise: a hole-injecting electrode; anelectron-injecting electrode paired with the hole-injecting electrode;and a functional layer provided between the hole-injecting electrode andthe electron-injecting electrode and emitting light by application of anelectric field produced by the electrodes, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains an electron-deficient substance for accepting electrons emittedfrom a low work function metal and a capturing substance for capturingthe low work function metal in its ionic state, the low work functionmetal being a metal other than a highest work function metal among themetals.

[0106] Still another lighting system of the present inventioncorresponding to the third aspect may comprise: an electron-injectingelectrode containing at least two or more different metals havingdifferent work functions; a hole-injecting electrode paired with theelectron-injecting electrode; a functional layer provided between theelectron-injecting electrode and the hole-injecting electrode andemitting light by application of an electric field produced by theelectrodes, wherein one of a capturing substance for capturing a lowwork function metal in its ionic state and an electron-deficientsubstance for accepting electrons emitted from the low work functionmetal is contained in the electron-injecting electrode and the other iscontained in the functional layer, the low work function metal being ametal other than a highest work function metal among the metals.

[0107] With the above-described configurations, planar light emitting,flexible lighting systems can be provided. Consequently, withoutbringing about a conventional loss of luminance in indirect lighting andthe like, new lighting systems can be provided and new lighting spacecan be created.

BRIEF DESCRIPTION OF THE DRAWINGS

[0108] Other objects, features, and advantages of the present inventionwill be understood upon review of the following description. Inaddition, the benefits of the present invention will become apparentfrom the following description taken in conjunction with theaccompanying drawings.

[0109]FIG. 1 is a schematic cross-sectional view showing a thin film ELdevice according to Embodiment 1 of the present invention.

[0110]FIG. 2 is a schematic cross-sectional view showing another thinfilm EL device according to Embodiment 1 of the present invention.

[0111]FIG. 3 is a schematic cross-sectional view showing still anotherthin film EL device according to Embodiment 1 of the present invention.

[0112]FIG. 4 is a schematic cross-sectional view showing yet anotherthin film EL device according to Embodiment 1 of the present invention.

[0113] FIGS. 5(a) and 5(b) are schematic cross-sectional views eachshowing a thin film EL device according to Embodiment 2 of the presentinvention; FIG. 5(a) shows a state in which an electron-deficientsubstance is uniformly distributed in a functional layer and FIG. 5(b)shows a state in which an electron-deficient substance is distributed ina functional layer with a concentration gradient.

[0114]FIG. 6 is a schematic cross-sectional view showing another thinfilm EL device according to Embodiment 2 of the present invention.

[0115]FIG. 7 is a schematic cross-sectional view showing a thin film ELdevice according to Embodiment 3 of the present invention.

[0116]FIG. 8 is a schematic cross-sectional view showing another thinfilm EL device according to Embodiment 3 of the present invention.

[0117]FIG. 9 is a schematic cross-sectional view showing still anotherthin film EL device according to Embodiment 3 of the present invention.

[0118]FIG. 10 is a schematic cross-sectional view showing yet anotherthin film EL device according to Embodiment 3 of the present invention.

[0119] FIGS. 11(a) and 11(b) are schematic cross-sectional views eachshowing a thin film EL device according to Embodiment 4 of the presentinvention; FIG. 11(a) shows a state in which an ion capturing substanceis uniformly distributed in a functional layer and FIG. 11(b) shows astate in which an ion capturing substance is distributed in a functionallayer with a concentration gradient.

[0120]FIG. 12 is a schematic cross-sectional view showing another thinfilm EL device according to Embodiment 4 of the present invention.

[0121]FIG. 13 is a schematic cross-sectional view showing a thin film ELdevice according to Embodiment 5 of the present invention.

[0122]FIG. 14 is a schematic cross-sectional view showing another thinfilm EL device according to Embodiment 5 of the present invention.

[0123] FIGS. 15(a) and 15(b) are schematic cross-sectional views eachshowing a thin film EL device according to Embodiment 6 of the presentinvention.

[0124]FIG. 16 is a schematic cross-sectional view showing another thinfilm EL device according to Embodiment 6 of the present invention.

[0125]FIG. 17 is a schematic cross-sectional view showing a prior artthin film EL device.

[0126]FIG. 18 is a schematic cross-sectional view showing another priorart thin film EL device.

BEST MODE FOR CARRYING OUT THE INVENTION

[0127] Embodiments of the present invention are described below.

Embodiment 1

[0128] An embodiment of a thin film EL device according to the presentinvention is described below. FIG. 1 is a schematic cross-sectional viewshowing a thin film EL device according to Embodiment 1.

[0129] As shown in the figure, a thin film EL device 10 according to thepresent embodiment has at least a hole-injecting electrode 12, anelectron-injecting electrode 14 paired with the hole-injecting electrode12, and a functional layer 13 provided between the hole-injectingelectrode 12 and the electron-injecting electrode 14, stacked on top ofeach other on a substrate 11.

[0130] The substrate 11 can be anything that can support theabove-described hole-injecting electrode 12 and the like. In addition,in the case where light emitted from the functional layer 13 isextracted from the side of the substrate 11, the substrate should havetransparency or translucency to visible light. Examples of such asubstrate include a glass substrate, such as, for example, Corning 1737(trade name, available from Corning Incorporated), and a resin filmsubstrate such as polyester.

[0131] The hole-injecting electrode 12 is an electrode that functions toinject holes into the functional layer 14. When light emitted from thefunctional layer 14 is extracted from the side of the substrate 11, thehole-injecting electrode 12 needs to have transparency or translucency.In such a case, an ITO (indium tin oxide) film, for example, can beutilized as the hole-injecting electrode 12. In addition to ITO, SnO(tin oxide), Ni (nickel), Au (gold), Pt (platinum), Pd (palladium) orthe like can also be utilized.

[0132] The film thickness of the hole-injecting electrode 12 isdetermined by the required sheet resistance and visible lighttransmittance. It should be noted, however, that the thin film EL devicehas a higher driving current density than, for example, the liquidcrystal display device, and thus it is preferable that the sheetresistance be low. For this reason, the hole-injecting electrode 12 isoften used with a film thickness of 100 nm or more.

[0133] The main function of the functional layer 13 is to emit light byapplication of an electric field. The functional layer 13 may becomposed of a single luminescent layer or may have a multilayerstructure composed of a plurality of layers stacked on top of each otherso as to divide functions. In the case of the multilayer structure, athin film EL device according to the present invention can employvarious configurations. In the following description, an example isprovided that shows a case where a hole-transport layer, a luminescentlayer, and an electron-transport layer are stacked in this order fromthe side of the substrate 11.

[0134] The hole-transport layer functions to receive holes from thehole-injecting electrode 12 and transport the holes to the luminescentlayer. In addition, the hole-transport layer functions to hinderelectron passage. Materials used for the hole-transport layer include:for example, tetraphenylbenzidine compounds, triphenylamine trimers, andbenzidine dimmers, disclosed in Japanese Unexamined Patent PublicationNo. 7-126615; various triphenyl diamine derivatives disclosed inJapanese Unexamined Patent Publication No. 8-48656;N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (MTPD)disclosed in Japanese Unexamined Patent Publication No. 7-65958; andtriphenylamine tetramers disclosed in Japanese Unexamined PatentPublication No. 10-228982. Further, of these materials exemplified,derivatives having triphenylamine as the basic skeleton are preferable,and in particular, triphenylamine tetramers are more preferable.

[0135] The electron-transport layer functions to receive electrons fromthe electron-injecting electrode 14 and transport the electrons to theluminescent layer. In addition, the electron-transport layer functionsto hinder hole passage. For materials used for the electron-transportlayer, for example, tris(8-quinolinolato)aluminum (hereinafter referredto as Alq) is preferable. In addition to Alq, other examples includemetal complexes, such as tris(4-methyl-8-quinolinolato)aluminum,3-(2′-benzothiazolyl)-7-diethylaminocoumarin, and the like. It should benoted that as materials for the hole-transport layer and theelectron-transport layer, inorganic materials that form a p-layer or ann-layer can also be employed in addition to the organic materials listedabove.

[0136] The film thicknesses of the hole-transport layer and theelectron-transport layer are preferably in the range of 10 to 1000 nm.In addition, each of these layers can be composed of a plurality oflayers. That is, when the hole-transport layer is formed from aplurality of layers, the layers can be stacked such that the ionizationpotential gradually. decreases toward the luminescent layer. When theelectron-transport layer is formed from a plurality of layers, thelayers can be stacked such that the electron affinity graduallyincreases toward the luminescent layer.

[0137] The luminescent layer is a layer in which holes injected from thehole-transport layer and electrons injected from the electron-transportlayer are combined together and the combined energy is emitted as light.Examples of the luminescent layer include a hole-transportingluminescent layer, an electron-transporting luminescent layer, a bipolarluminescent layer, and the like. For materials used for the luminescentlayer, in addition to the above-described Alq or its derivatives, it isalso possible to use one in which compounds such as Alq or itsderivatives are doped with a dye such as coumarin 6, DCM(4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran), orphenoxazone 9. Further, one in which triphenylamine is doped withrublene can also be employed. Moreover, in addition to theabove-described organic materials, inorganic fluorescent materials canalso be used. When using inorganic fluorescent materials, for example,an inorganic fluorescent material is dispersed in a polymer matrix andthe dispersion is coated, thereby forming a layer.

[0138] In the foregoing, the functional layer 13 was described, as anexample, for the case of a multilayer structure consisting of thehole-transport/luminescent/electron-transport layers; however, thepresent invention is not limited thereto. For example, a multilayerstructure consisting of the luminescent/electron-transport orhole-transport/luminescent layers or a multilayer structure consistingof the hole-transport/carrier-blocking/electron-transport layers may beemployed. Further, it is also possible to employ a multilayer structurein which a hole-blocking layer such as bathocuproine is stacked betweena hole-transport layer and an electron-transport layer so that thehole-transport layer emits light. In addition, the functional layer maybe composed of a single luminescent layer.

[0139] As for the layers composing the functional layer 13, such as thehole-transport layer, the electron-transport layer, and the luminescentlayer, it is preferable that each layer have an amorphous andhomogeneous film structure. This is because when the film structure iscrystallized, it becomes necessary to increase the driving voltage ofthe device, and at the same time the injection efficiency of chargecarriers is reduced, causing degradation of the device characteristics.

[0140] The electron-injecting electrode 14 is formed from a metal layer15 containing at least two or more different metals having differentwork functions and an electron-deficient substance layer 16 containingan electron-deficient substance and has a basic function of injectingelectrons into the functional layer 13.

[0141] The metal layer 15 can be composed, for example, of an alloycomposed of a metal with a low work function and a low electroninjection barrier and a stable metal with a higher work function thanthe foregoing metal. In addition, the metal layer may be a multilayerelectrode, which will be described later, having a plurality of metalfilms stacked on top of each other.

[0142] Examples of the alloy include an Mg—Ag alloy proposed by Tang etal., an Al—Li alloy and the like. In addition, it is also possible toemploy a Ca—Ag alloy, an Li—Al—Zn alloy, a Ca—Al alloy, an Mg—Al alloy,an Sn—Al—Li alloy, a Bi—Al—Li alloy, an In—Al—Li alloy, and the like.The above-described metal with a low work function (low work functionmetal) indicates a metal that has a relatively low work function ascompared with the above-described stable metal. Specifically, alkalimetals including Li, Na, K, Rb, Cs, and Fr, alkaline earth metalsincluding Be, Mg, Ca, Sr, Ba, and Ra, and the like are preferable. Theselow work function metals have a tendency to readily emit electrons andtherefore electron can be injected into the inside the luminescent layerextremely readily, making it possible to increase the luminance of thethin film EL device. It should be noted that electrons emitted from thelow work function metal are valence electrons in the outermost shell;for example, in an alkali metal such as Li, electrons in the 2 s orbitalare emitted, and in an alkaline earth metal such as Na, electrons in the3 s orbital are emitted, and thus the low work function metal becomes acation (positive ion).

[0143] Moreover, the electron-injecting electrode 14 contains a metalhaving a higher work function than the low work function metal. Themetal with a higher work function serves to protect and prevent the lowwork function metal from deteriorating. The low work function metal hasa high reactivity with moisture, oxygen, and the like, and thus byallowing the low work function metal to form an alloy with a more stablemetal, the low work function metal can be protected from moisture andthe like in the air. As a result, electrons can be stably injected intothe functional layer 13. Here, examples of metals with high workfunctions include Al, Zn, Ag, In, Sn, Bi, Pd, Cu, and the like.

[0144] The electron-deficient substance layer 16 contains at least anelectron-deficient substance. The electron-deficient substance is asubstance that is deficient in the number of valence electrons comparedto the number of valence orbitals. For the electron-deficient substance,it is possible to utilize various electron-deficient organic metalcompounds or electron-deficient inorganic metal compounds, obtained as aresult of multicenter bonding between an atom, which easily composes anelectron-deficient substance such as Li, Be, Mg, B, Zn, and Al, andanother atom.

[0145] Examples of the electron-deficient organic metal compoundsinclude alkylated Al which is stabilized with 3-center-2-electron bondsbeing formed and a compound represented by the following chemicalformula (1).

[0146] The R¹ and R² each independently is a bridging ligand containinga nitrogen-containing aromatic ring or its derivative which has at leastone nitrogen atom as coordinating atom, halogen, or a bridging ligandcontaining alkyl of 1 to 3 carbons. In the bridging ligand containing anitrogen-containing aromatic ring which has at least one nitrogen atom,examples of the bridging ligand containing a nitrogen-containingaromatic ring which has one nitrogen atom include pyrrole, pyridine,oxazole, 3,3′-bipyridine-5,5′-diyl, and the like. In addition, examplesof the bridging ligand containing a nitrogen-containing aromatic ringwhich has two or more nitrogen atoms include imidazole, pyrazole,pyridazine, pyrazine, pyrimidine, phthalazine, 1H-indazole, oxadiazole,9,10-phenanthroline, triazole, triazine, tetrazine, tetrazole, and thelike. Further, examples of the halogen include F, Cl, Br, I, and At.Moreover, examples of the bridging ligand containing alkyl of 1 to 3carbons include methyl, ethyl, and butyl.

[0147] The R³, R⁴, R⁵, and R⁶ are each independently is one selectedfrom the group consisting of hydrogen, alkyl, an aryl derivative, and aderivative of a nitrogen-containing aromatic ring that contains onenitrogen atom as coordinating atom, and examples of the alkyl includemethyl, ethyl, and the like. In addition, examples of the arylderivative include phenyl, tolyl, pyridyl, triazole, tetrazole,indazole, and the like. Further, examples of the derivative of anitrogen-containing aromatic ring include pyrrole, indole, isoindole,carbazole, and the like. The M¹ is a metallic or semi-metallic elementselected from a group of atoms consisting of Be, Mg, Ca, B, Al, and Ga.

[0148] Specific examples of compounds represented by the chemicalformula (1) include 4,4,8,8-tetraethylpyrazabole,1,3,5,7-tetramethylpyrazabole, pyrazabole, and the like.

[0149] Examples of electron-deficient inorganic metal compounds includeLiH, BeH₂, and the like. Particularly, in the case where the functionallayer 13 which contacts with the cathode is composed of an organiccompound, the above-described organic metal complex compounds arepreferable.

[0150] These electron-deficient substances have not completed a closedshell and therefore have strong electron-accepting properties andexcellent electron transport properties. Thus, in the prior art,electron-deficient substances were sometimes used as electron-injectingmaterial, without using low work function metals.

[0151] For reference, it should be noted that at the present time, forthe description of the bonds between neutral molecules, theLewis-Langmuir's theory of valency and the octet theory are utilized,but as for the electron-deficient substance, it is difficult to describethe bonding state by applying such theories However, by a theory inwhich molecular orbitals are formed from the combination of some atomicorbitals, electron-deficient substances can be described easily. A moredetailed description of electron-deficient substances is provided ininorganic chemistry books, dictionaries of physics and chemistry, and soforth.

[0152] The idea of providing in the electron-injecting electrode 14 theelectron-deficient substance layer 16 containing an electron-deficientsubstance such as those described above came about from thedeterioration mechanism of low work function metals, which will bedescribed below, investigated by the present inventors.

[0153] Using Li as an example of a low work function metal, thedeterioration control mechanism of low work function metals isdescribed. First, Li which is contained in the electron-injectingelectrode 14 emits electron(s) and becomes an Li cation, as is shown inthe following reaction formula (3).

Li⇄Li ⁺ +e ⁻  (3)

[0154] When the reaction formula (3) performs electron transfercontinuously and reversibly, Li deterioration essentially does notoccur. The Li cation, however, is highly reactive and has a strongoxidizing action. Thus, the Li cation easily reacts, at its formation,with nitrogen and the like present in the device or in the storageenvironment of the device. That is, a nitride (insulator) of Li isformed and thus the reaction formula (3) becomes irreversible.Consequently, a stable electron-injection function to the functionallayer 13 is reduced, bringing about device degradation.

[0155] On the other hand, when electrons are injected into theelectron-deficient substance layer 16 from the metal layer 15, becausean electron-deficient substance is a strong Lewis acid, the electronsare captured by the electron-deficient substance. Thereby, an anion (A⁻)is formed.

A+e ⁻ ⇄A ⁻  (4)

[0156] In the above formula, A represents an electron-deficientsubstance.

[0157] Here, because A⁻ can satisfy the octet rule by acceptingelectrons, a forward reaction is more likely to occur. Hence, thesubstance can exist continuously and stably in its anionic state.Consequently, the electron-deficient substance layer 16 containing anelectron-deficient substance functions as a layer having an extremelyexcellent electron transport property, making it possible to inject moreelectrons into the luminescent layer. Thereby, the recombination rate ofholes and electrons is increased, improving electroluminescentefficiency.

[0158] Furthermore, the A⁻ acts as a weak Lewis base to the Li cation,and thus a reaction represented by the following reaction formula (5)occurs at the boundary between the electron-injecting electrode 14 andthe electron-deficient substance layer 16, thereby forming complexes. Inaddition, because part of the Li cations enter into theelectron-deficient substance layer 16 by ablation, a reaction occurseven inside the electron-deficient substance layer 16.

A+Li ⁺ ⇄[A ⁻ Li ⁺]  (5)

[0159] Next, the substance is further transferred from an ioncomplex-like intermediate to a neutral molecule of a Lewis acid (A) andLi. In other words, the electron-deficient substance prevents the lowwork function metal from changing into an oxide, a nitride, or the like,and thus high electron injection efficiency of the electron-injectingelectrode 14 can be maintained. Consequently, while light emission withhigh luminance is realized, the lifetime of the device can be increased.

[0160] The average film thickness of the electron-deficient substancelayer 16 is preferably in the range of 0.1 to 100 nm. This is becausewhen the electron-deficient substance layer is in a monolayer structurehaving a substantially uniform film thickness, the film thickness,thought it varies with the type of the electron-deficient substance,results in on the order of 0.1 nm or more, making it difficult to formthe electron-deficient substance layer 16 having a film thicknesssmaller than that. On the other hand, a film thickness of greater than100 nm increases the applied voltage, bringing about device degradation,and thus is not desirable.

[0161] Now, a fabrication method of a thin film EL device according toEmbodiment 1 is described.

[0162] First, on a substrate 11, a hole-injecting electrode 12 is formedin a conventional manner. Specifically, when, for example, thehole-injecting electrode 12 is an ITO film, film-forming techniques suchas sputtering, electron beam evaporation, or ion plating can beemployed. These film-forming techniques allow improvement intransparency of the ITO film and reduction in resistivity.

[0163] Subsequently, on the electron-injecting electrode 14, afunctional layer 13 is formed. The functional layer can employ variousconfigurations as discussed earlier. For example, when forming ahole-transport layer, a luminescent layer, and an electron-transportlayer in this order from the side of the functional layer 13, it ispreferable to employ vacuum vapor deposition as the film-formingtechnique for the layers. With this technique, formation of an amorphousand homogeneous thin film is made possible. Further, when the layers areformed continuously in vacuum, it is possible to prevent impurities fromadhering to the boundaries between the layers. Consequently, improvementof characteristics such as a reduction in operating voltage, an increasein efficiency, and an increase in lifetime can be achieved. In addition,in forming these layers by vacuum vapor deposition, when any of thelayers contains a plurality of compounds, it is preferable that boats(containers filled with parent materials for deposition), having thereineach compound, be co-deposited as individually controlling thetemperatures. It is also possible to deposit a mixture in which thesecompounds are mixed together in advance. Further, for other film-formingtechniques than the vacuum vapor deposition, it is also possible toemploy solution coating techniques such as spin coating, dipping, andcasing, Langmuir-Blodgett (LB) technique, and the like. In the case ofthe solution coating techniques, such techniques may be performed bydispersing each compound in a matrix substance such as polymer.

[0164] Next, on the functional layer 13, an electron-deficient substancelayer 16 is formed by vacuum vapor deposition. Deposition conditions arenot particularly limited and thus are appropriately set so that adesired thin film is formed. Specifically, when depositing underconditions, for example, where the deposition rate is 0.01 to 0.5 nm/secand the vacuum pressure is 10³ to 10⁶ Pa, the electron-deficientsubstance layer 16 with a good film structure can be formed.

[0165] Subsequently, on the electron-deficient substance layer 16, ametal layer 15 is formed, for example, by deposition or sputtering. Atthis point, a low work function metal is changed into an oxide, anitride, or the like during the formation process of the metal layer 15,that is, the deterioration of the metal is already underway at thebeginning of the device fabrication process. Due to this, conventionaldevices had lower light-emission luminance than the theoreticallypredicted value.

[0166] However, in the present embodiment, since the metal layer 15 isformed on the electron-deficient substance layer 16, the deteriorationof the low work function metal can be prevented. A more detaileddescription is as follows. The low work function metal emits electronsand becomes a cation even during the film formation process. The emittedelectrons are accepted by the electron-deficient substance, therebyforming an anion of the electron-deficient substance. The anion, beforethe cation is changed into an oxide or the like by reacting with water,oxygen, or the like, performs electron transfer with the cation and as aresult, charge transfer occurs. Thereby, the low work function metalreturns to the ground state, which in turn inhibits the low workfunction metal from changing into an oxide or the like anddeteriorating. This enables the formation of the metal layer 15containing very few oxides or the like, allowing the device to emitlight with high luminance.

[0167] Furthermore, as described above, the deterioration of the lowwork function metal can be prevented, and thus it is also possible tomake the film thickness of the metal layer 15 even thinner.Consequently, good workability is achieved. In addition, variations inlight-emission luminance in the plane can be controlled, and thus it ispossible to fabricate a device with good reproducibility and to improveyield.

[0168] Thus, with the fabrication method of a thin film EL deviceaccording to Embodiment 1, a thin film EL device with extremely highlight-emission luminance compared with a conventional thin film ELdevice can be fabricated with good workability and good reproducibility.

[0169] When a thin film EL device has a pn junction, the thin film ELdevice has an electromotive force, and therefore even in a state whereelectricity is not turned on, electron transfer is performed in thedevice. Hence, it can be assumed that even in a storing state with noload, the reactions of the above-described reaction formulae (3) to (5)are proceeded. Further, the reactions of the reaction formulae (3) to(5) occur even in the fabrication process of the thin film EL devicehaving a pn junction. Thus, in this case too, a thin film EL device withhigh light-emission luminance can be fabricated with good workabilityand reproducibility, while improving yield.

[0170] It should be noted that in the present embodiment theelectron-injecting electrode 14 was described, as an example, for thecase where the electrode is formed from the metal layer 15 containing analloy and the electron-deficient substance layer 16, but the presentinvention is not limited thereto. For example, as shown in FIG. 2, anelectron-injecting electrode 14 may be a multilayer electrode having anelectron-deficient substance layer 16, a low work function metal layer17 containing a low work function metal, and a passivating metal layer18 containing a metal with a higher work function than the low workfunction metal, stacked in this order from the side of a functionallayer 13. In this case, the low work function metal layer 17 and thepassivating metal layer 18 can be formed by deposition, sputtering, orthe like.

[0171] Furthermore, as shown in FIG. 3, an electron-injecting electrode14 may be a multilayer electrode having an electron-deficient substancelayer 16 containing a low work function metal 21 and a passivating metallayer 18, stacked in this order from the side of a functional layer 13.In this case, the film thickness of the electron-deficient substancelayer 16 is preferably in the range of 0.1 to 1000 nm. This is becausewhen the electron-deficient substance layer 16 is in a monolayerstructure having a substantially uniform film thickness, the filmthickness, though it varies with the type and content of theelectron-deficient substance, results in on the order of 0.1 nm or more,making it difficult to form the electron-deficient substance layer 16having a film thickness smaller than that. On the other hand, a filmthickness of greater than 1000 nm increases the applied voltage,bringing about device degradation, and thus is not desirable. Further,the concentration of the electron-deficient substance should be in therange of 30 to 99 mol %. A concentration of 30 mol % or less is notdesirable because with such a concentration the electron transportproperty cannot be sufficiently improved and the deterioration of thelow work function metal cannot be prevented On the other hand, aconcentration of 99 mol % or more relatively reduces the ratio of thelow work function metal, reducing the amount of electrons to beinjected, and thus is not desirable. The electron-deficient substancelayer 16 can be formed by co-depositing an electron-deficient substanceand a low work function metal. A passivating metal layer 18 can beformed by deposition, sputtering, or the like, as the above-describedcase.

[0172] Moreover, as shown in FIG. 4, an electron-injecting electrode 14may be a single layer containing an electron-deficient substance 20, alow work function metal 21, and a metal with a higher work function thanthe low work function metal 21. In this case, as the film-formingtechnique for the electron-injecting electrode 14, co-deposition can beemployed.

[0173] It should be noted that in the present embodiment theelectron-deficient substance layer 16 was described, as an example, forthe case of a multilayer structure, but the present invention is notlimited thereto. For example, in a thin film EL device shown in FIG. 1,an electron-deficient substance layer can be provided in an islandconfiguration between the functional layer 13 and the metal layer 15. Inaddition, in a thin film EL device shown in FIG. 2, anelectron-deficient substance layer can be provided in an islandconfiguration between the functional layer 13 and the low work functionmetal layer 17. Even with these configurations, it is possible toinhibit deterioration of the low work function metal and to improve thelight-emission lifetime of the device.

Embodiment 2

[0174] Another embodiment of a thin film EL device according to thepresent invention is described below. It should be noted that thecomponents having the same functions as those of the thin film EL deviceof Embodiment 1 are designated by the same reference numerals and thuswill not be further described.

[0175] Thin film EL devices according to Embodiment 2 are different fromthin film EL devices according to Embodiment 1 in that anelectron-deficient substance is contained in the functional layer butnot in the electron-injecting electrode.

[0176]FIG. 5(a) is a cross-sectional view schematically showing a thinfilm EL device according to Embodiment 2 and shows a state in which anelectron-deficient substance is distributed in a functional layer. Anelectron-injecting electrode 22 shown in the figure is a metal layercontaining an alloy composed of at least two or more different metalshaving different work functions. In addition, a functional layer 23basically has the same function as the functional layer according toEmbodiment 1, but in the present embodiment, the functional layerfurther contains an electron-deficient substance 20. Theelectron-deficient substance 20 is distributed in the functional layer23 on the side of the electron-injecting electrode 22. The area wherethe electron-deficient substance 20 is present should be within abouttwo-thirds of the film thickness of the functional layer 23 from theboundary between the electron-injecting electrode 22 and the functionallayer 23. Here, the film thickness of the functional layer 23 is, forexample, 50 to 1000 nm. It should be noted that the electron-deficientsubstance 20 may be uniformly distributed throughout the functionallayer 23.

[0177] When, for example, the functional layer is formed from ahole-transport layer, a luminescent layer, and an electron-transportlayer, stacked in this order from the hole-injecting electrode side, anelectron-deficient substance 20 is contained at least in theelectron-transport layer. In the electron-transport layer, anionic(radical) molecules are continuously formed by electron transfer betweenadjacent molecules, and the electrons are transported hopping in thelayer. Meanwhile, in the case of conventionally-used electron transportmaterials, the stability is high in the ground state and therefore evenif the materials accept electrons and fall into an anionic (radical)state, the materials quickly returns to the ground state. That is, areverse reaction in which electrons are emitted is likely to occur. Onthe contrary, anions formed from an electron-deficient substance cansatisfy the octet rule by accepting more electrons and thus a forwardreaction is likely to occur. Thereby, the substance can existcontinuously and stably in its anionic state. As can be seen from this,the electron-deficient substance has an extremely excellent electrontransport property, resulting in a good electron transport to thefunctional layer 23. Consequently, the device can emit light with highluminance, and at the same time electroluminescent efficiency can beimproved.

[0178] It is also possible to distribute an electron-deficient substance20 in the functional layer such that, as shown in FIG. 5(b), theconcentration of the substance gradually increases toward anelectron-injecting electrode 22. The reaction between the anions (A−) ofthe electron-deficient substance and the cations of the low workfunction metal occur more frequently at the boundary between thefunctional layer 23 and the electron-injecting electrode 22. Though partof the cations enter into the functional layer 23 by ablation, becausethe number of the cations gradually decreases toward the center of thefunctional layer 23, the frequency of the reaction between the anions ofthe electron-deficient substance and the cations decreases accordingly.Thus, when a concentration gradient is established, as in theabove-described configuration, electrons can be efficiently donated tothe cations of the low work function metal.

[0179] The concentration of the electron-deficient substance 20 ispreferably in the range from 0.1 mol % to 99.9 mol %. When theconcentration is less than 0.1 mol %, the electron transport propertycannot be improved. On the other hand, when the concentration is greaterthan 99.9 mol %, the layer becomes extremely close to a single layercomposed of an electron-deficient substance, and as a result, thefunctional layer 23 cannot fully exert the light-emitting function.Further, in the case where the electron-deficient substance 20 isuniformly distributed in the functional layer within a given area fromthe boundary between the functional layer 23 and the electron-injectingelectrode 22, or in the case where electron-deficient substance 20 isuniformly distributed throughout the functional layer 23, it ispreferable that the concentration of the electron-deficient substance 20be in the range from 0.1 mol % to 50.0 mol %.

[0180] The functional layer 23 having the electron-deficient substance20 distributed therein is formed in the following manner. First, aportion of a functional layer 23 that is not supposed to contain anelectron-deficient substance 20 is formed, by deposition, on ahole-injecting electrode 12. Subsequently, an electron-deficientsubstance and a functional layer material are co-deposited ascontrolling the deposition rate so as to obtain a specified mixingratio. Thereby, a functional layer 23 can be formed in which theelectron-deficient substance 20 is uniformly distributed in thefunctional layer on the side of an electron-injecting electrode 22,within a given area. On the other hand, for formation of a functionallayer 23 having an electron-deficient substance 20 distributed thereinsuch that the concentration of the substance gradually increases towardan electron-injecting electrode 22, the layer can be formed byincreasing the deposition temperature (specifically, by increasing theamount of electric current).

[0181] It should be noted that the functional layer 23 may contain, asshown in FIG. 6, a low work function metal 21 as well as anelectron-deficient substance 20. In this case, it is also possible todistribute the low work function metal 21 in the functional layer suchthat the concentration of the metal gradually increases toward anelectron-injecting electrode 22. Here, the content of the low workfunction metal 21 can be set in the range from 0.01 weight % to 99.9weight %. Acontent of less than 0.01 weight % reduces theelectron-injection function, reducing electroluminescent efficiency, andthus is not desirable. On the other hand, when the content is greaterthan 99.9 weight %, the layer becomes extremely close to a single layercomposed of a low work function metal, and as a result, the functionallayer 23 cannot fully exert the light-emitting function.

[0182] Furthermore, the electron-injecting electrode 22 may be amultilayer electrode having a low work function metal layer containing alow work function metal and a passivating metal layer containing a metalwith a higher work function than the low work function metal, stacked inthis order from the side of a functional layer 23.

Embodiment 3

[0183] Still another embodiment of a thin film EL device according tothe present invention is described below. It should be noted that thecomponents having the same functions as those of the thin film EL deviceof Embodiment 1 are designated by the same reference numerals and thuswill not be further described.

[0184] Thin film EL devices according to Embodiment 3 are different fromthin film EL devices according to Embodiment 1 in that a capture layercontaining a capturing substance is provided in place of theelectron-deficient substance layer containing an electron-deficientsubstance. A more detailed description is as follows.

[0185]FIG. 7 is a schematic cross-sectional view showing a thin film ELdevice according to Embodiment 3.

[0186] As shown in the figure, a thin film EL device 30 according toEmbodiment 3 has at least a hole-injecting electrode 12, anelectron-injecting electrode 31 paired with the hole-injecting electrode12, and a functional layer 13 provided between the hole-injectingelectrode 12 and the electron-injecting electrode 31, stacked on top ofeach other on a substrate 11.

[0187] The electron-injecting electrode 31 is formed from a metal layer15 and a capture layer 32 containing a capturing substance and has abasic function of injecting electrons into the functional layer 13.

[0188] The capture layer 32 contains at least a capturing substance. Thecapturing substance is a substance that is capable of forming acoordinate bond in which an unshared pair of electrons of the capturingsubstance is donated to a cation of the low work function metal to sharethe unshared pair of electrons.

[0189] Examples of atoms which compose the capturing substance and towhich unshared pairs of electrons belong include oxygen, sulfur,selenium, nitrogen, phosphorus, arsenic, and the like.

[0190] In addition, heterocyclic compounds that contain such atoms maybe used. In this case, examples of heteroatoms in heterocycles includeoxygen, sulfur, nitrogen, arsenic, and the like. The capturing substancemay be compounds that contain functional groups such as carbonyl groups,amino groups, imino groups, and thiocarbonyl groups. Further, achelating agent such as 1,10-phenanthroline may also be used which hastwo or more of such functional groups and allows the ion of the low workfunction metal to have a multidentate ligand.

[0191] In particular, electron-accepting capturing substances thataccept electrons are most preferable, and an example of suchelectron-accepting capturing substances includes a compound representedby the following chemical formula (2).

[0192] The R⁷ and R⁸ are each independently is a bridging ligandcontaining a nitrogen-containing aromatic ring or a derivative thereofwhich has at least one nitrogen atom as coordinating atom, halogen, or abridging ligand containing alkyl of 1 to 3 carbons. In the bridgingligand containing a nitrogen-containing aromatic ring which has at leastone nitrogen atom, examples of the bridging ligand containing anitrogen-containing aromatic ring which has one nitrogen atom includepyrrole, pyridine, oxazole, 3,3′-bipyridine-5,5′-diyl, and the like. Inaddition, examples of the bridging ligand containing anitrogen-containing aromatic ring which has two or more nitrogen atomsinclude imidazole, pyrazole, pyridazine, pyrazine, pyrimidine,phthalazine, 1H-indazole, oxadiazole, 9,10-phenanthroline, triazole,triazine, tetrazine, tetrazole, and the like. Further, examples of thehalogen include F, Cl, Br, I, and At. Moreover, examples of the bridgingligand containing alkyl of 1 to 3 carbons include methyl, ethyl, andbutyl.

[0193] The R⁹, R¹⁰, R¹¹, and R¹² are each independently is one selectedfrom the group consisting of hydrogen, alkyl, an aryl derivative, and aheterocyclic derivative, and at least one of R⁹ to R¹² is a ligandhaving an unshared pair of electrons. Examples of the alkyl includemethyl, ethyl, and the like. In addition, examples of the arylderivative include phenyl, tolyl, pyridyl, triazole, tetrazole,indazole, and the like. Further, examples of the heterocyclic derivativeinclude pyrrole, pyridine, oxazole, 3,3′-bipyridine-5,5′-diyl,imidazole, pyrazole, pyridazine, pyrazine, pyrimidine, phthalazine,1H-indazole, oxadiazole, 9,10-phenanthroline, triazole, triazine,tetrazine, tetrazole, and the like.

[0194] The M² is a metallic or semi-metallic element selected from agroup of atoms consisting of Be, Mg, Ca, B, Al, and Ga.

[0195] A specific example of the compound represented by the chemicalformula (2) includes 4,4,8,8-tetrakis(1H-pyrazole-1-yl)pyrazabole(hereinafter referred to as PPZB) represented by the following chemicalformula (6).

[0196] It should be noted that the portion circled with a broken line inthe chemical formula (6) has a pyrazabole structure. This pyrazabolestructure is a ring structure in which two bridging ligands (pyrazole)are respectively bonded to two borons by the bridging bond. Since theportion of the bridging bond has an insufficient number of electrons,PPZB is a kind of electron-deficient substances. Thus, PPZB has anelectron-accepting property.

[0197] The technical significance of the provision of the capture layer32, which contains a capturing substance such as that described above,in the electron-injecting electrode 14 is as follows.

[0198] Using an example in which PPZB is used as a capturing substanceand Li as a low work function metal, the deterioration control mechanismof the low work function metal is described. As was discussed inEmbodiment 1, Li which is contained in an electron-injecting electrode14 emits electrons and becomes an Li cation (see the reaction formula(3)).

[0199] PPZB donates an unshared pair of electrons to the Li cation andforms another ring structure (chelate ring), as shown in the chemicalformula (7) below, such that the Li (cation) is coordinated as beingsandwiched. The chelate complex thus produced has a highly stablestructure because of its steric effect.

[0200] Accordingly, the provision of the capture layer 32 prevents thelow work function metal such as Li from becoming an insulator such as anoxide or a nitride and allows electrons to be stably supplied to thefunctional layer 13. Consequently, while light emission with highluminance is realized, the lifetime of the device can be increased.

[0201] PPZB is also an electron-deficient substance and thus has anexcellent electron transport property; as a result, it is also possibleto inject more electrons into the luminescent layer.

[0202] The average film thickness of the capture layer 32 is preferablyin the range of 0.1 to 100 nm. This is because when the capture layer 32is in a monolayer structure having a substantially uniform filmthickness, the film thickness, thought it varies with the type of thecapturing substance, results in on the order of 0.1 nm or more, makingit difficult to form the capture layer 32 having a film thicknesssmaller than that. On the other hand, a film thickness of greater than100 nm increases the applied voltage, bringing about device degradation,and thus is not desirable.

[0203] Now, a fabrication method of a thin film EL device according toEmbodiment 2 is described.

[0204] First, in the same manner as described in Embodiment 1, ahole-injecting electrode 12 is formed on a substrate 11, and then on theelectron-injecting electrode 14 a functional layer 13 is formed.

[0205] Next, on the functional layer 13, a capture layer 32 is formed byvacuum vapor deposition. Deposition conditions are not particularlylimited and thus are appropriately set so that a desired film structureis formed. Specifically, when depositing under conditions, for example,where the deposition rate is 0.01 to 0.5 nm/sec and the vacuum pressureis 10³ to 10⁶ Pa, the capture layer 32 with a good film structure can beformed.

[0206] Subsequently, on the capture layer 32, a metal layer 15 isformed, for example, by deposition or sputtering. At this point, the lowwork function metal is changed into an oxide, a nitride, or the likeduring the formation process of the metal layer 15, that is, thedeterioration of the metal is already underway at the beginning of thedevice fabrication process. Due to this, conventional devices had lowerlight-emission luminance than the theoretically predicted value.

[0207] However, in the present embodiment, since the metal layer 15 isformed on the capture layer 32, the deterioration of the low workfunction metal can be prevented. A more detailed description is asfollows. The low work function metal emits electrons and becomes acation even during the film formation process. The metal cation, beforebecoming an oxide or a nitride by reacting with water, oxygen, and thelike, is captured by the capturing substance. Thereby, the metal layer15 can be formed as preventing deterioration of the low work functionmetal, allowing light emission with high luminance.

[0208] Furthermore, the prevention of the deterioration of the low workfunction metal allows the film thickness of the metal layer 15 to bemade even thinner, thereby achieving good workability. In addition,variations in light-emission luminance in the plane can be controlled,and thus it is possible to fabricate a device with good reproducibilityand to improve yield.

[0209] As described above, with the fabrication method of a thin film ELdevice according to Embodiment 2, a thin film EL device with extremelyhigh light-emission luminance compared with a conventional thin film ELdevice can be fabricated with good workability and good reproducibility.

[0210] It should be noted that in the present embodiment theelectron-injecting electrode 31 was described, as an example, for thecase where the electrode is formed from the metal layer 15 containing analloy and the capture layer 32, but the present invention is not limitedthereto. For example, as shown in FIG. 8, an electron-injectingelectrode 14 may be a multilayer electrode having a capture layer 32, alow work function metal layer 17, and a passivating metal layer 18,stacked in this order from the side of a functional layer 13.

[0211] Furthermore, as shown in FIG. 9, an electron-injecting electrode31 may be a multilayer electrode having a capture layer 32 containing alow work function metal 21 and a passivating metal layer 18, stacked inthis order from the side of a functional layer 13. In this case, thefilm thickness of the capture layer 32 is preferably in the range of 0.1to 1000 nm. This is because when the capture layer 32 is in a monolayerstructure having a substantially uniform film thickness, the filmthickness, though it varies with the type of the capturing substance,results in on the order of 0.1 nm or more, making it difficult to formthe capture layer 32 having a film thickness smaller than that. On theother hand, a film thickness of greater than 1000 nm increases theapplied voltage, bringing about device degradation, and thus is notdesirable. Further, the concentration of the capturing substance shouldbe in the range of 30 to 99 mol %. A concentration of 30 mol % or lessis not desirable because with such a concentration the electrontransport property cannot be sufficiently improved and the deteriorationof the low work function metal cannot be prevented. On the other hand, aconcentration of 99 mol % or more relatively reduces the ratio of thelow work function metal, reducing the amount of electrons to beinjected, and thus is not desirable. The capture layer 34 can be formedby co-depositing a capturing substance and a low work function metal.The passivating metal layer 18 can be formed by deposition, sputtering,or the like, as the above-described case.

[0212] Moreover, as shown in FIG. 10, an electron-injecting electrode 31may be a single layer containing a capturing substance 33, a low workfunction metal 21, and a metal with a higher work function than the lowwork function metal 21. In this case, as the film-forming technique forthe electron-injecting electrode 31, co-deposition can be employed.

[0213] It should be noted that in the present embodiment the capturelayer 32 was described, as an example, for the case of a multilayerstructure, but the present invention is not limited thereto. Forexample, a capture layer may be provided in an island configurationbetween the capture layer 32 and the metal layer 15 or between thecapture layer 32 and the low work function metal layer 17. Even withsuch configurations, it is possible to inhibit deterioration of the lowwork function metal and to improve the light-emission lifetime of thedevice.

Embodiment 4

[0214] Yet another embodiment of a thin film EL device according to thepresent invention is described below. It should be noted that thecomponents having the same functions as those of the thin film EL deviceof Embodiment 3 are designated by the same reference numerals and thuswill not be further described.

[0215] Thin film EL devices according to Embodiment 4 are different fromthin film EL devices according to Embodiment 3 in that a capturingsubstance is contained in the functional layer but not in theelectron-injecting electrode.

[0216]FIG. 11(a) is a schematic cross-sectional view showing a thin filmEL device according to Embodiment 4 and shows a state in which acapturing substance is uniformly distributed in a functional layer. Anelectron-injecting electrode 35 shown in the figure is a metal layercontaining an alloy composed of at least two or more different metalshaving different work functions. A functional layer 36 basically has thesame function as the functional layer according to Embodiment 1, but inthe present embodiment, the functional layer further contains acapturing substance 33. The capturing substance 33 is provided so as tobe distributed in the functional layer 36 on the side of theelectron-injecting electrode 35. The area where the capturing substance33 is present should be in the range of about two-thirds of thefunctional layer 36 from the boundary between the functional layer 36and the electron-injecting electrode 35. Here, the film thickness of thefunctional layer 36 is, for example, 50 to 1000 nm.

[0217] It should be noted that the capturing substance 33 may beuniformly distributed throughout the functional layer 36.

[0218] Furthermore, the capturing substance 33 can be distributed in thefunctional layer, as shown in FIG. 11(b), such that the concentration ofthe substance gradually increases toward an electron-injecting electrode35. The reaction between the capturing substance and the cations of thelow work function metal occurs more frequently at the boundary betweenthe functional layer 36 and the electron-injecting electrode 35. Thoughpart of the cations enter into the functional layer 36 by ablation,because the number of the cations gradually decreases toward the centerof the functional layer 36, the frequency of the reaction between thecapturing substance and the cations decreases accordingly. Thus, when aconcentration gradient is established, as in the above-describedconfiguration, electrons can be efficiently donated to the cations ofthe low work function metal.

[0219] The concentration of the capturing substance 33 is preferably inthe range from 0.1 mol % to 99.9 mol %. When the concentration is lessthan 0.1 mol %, the cations of the low work function metal cannot becaptured sufficiently due to coordinate bonds or the like. On the otherhand, when the concentration is greater than 99.9 mol %, the layerbecomes extremely close to a single layer composed of the capturingsubstance, and as a result, the functional layer 36 cannot fully exertthe light-emitting function. Further, when the capturing substance 33 isuniformly distributed in the functional layer within a given area fromthe boundary between the functional layer 36 and the electron-injectingelectrode 35, or when the capturing substance 33 is uniformlydistributed throughout the functional layer 36, the concentration of thecapturing substance 33 is preferably in the range from 0.1 mol % to 50.0mol %.

[0220] It should be noted that the functional layer 36 can also containa low work function metal 21 as well as a capturing substance 33, asshown in FIG. 12. In this case, it is also possible to distribute thelow work function metal 21 in the functional layer such that theconcentration of the metal gradually increases toward anelectron-injecting electrode 35. Here, the content of the low workfunction metal 21 should be in the range from 0.01 weight % to 99.9weight %. A content of less than 0.01 weight % reduces theelectron-injection function, reducing electroluminescent efficiency, andthus is not desirable. On the other hand, when the content is greaterthan 99.9 weight %, the layer becomes extremely close to a single layercomposed of the low work function metal, and as a result, the functionallayer 36 cannot fully exert the light-emitting function.

[0221] Furthermore, the electron-injecting electrode 35 may be amultilayer electrode having a low work function metal layer and apassivating metal layer, stacked in this order from the side of thefunctional layer 36.

[0222] The functional layer 36 having the capturing substance 33distributed therein can be formed in the same manner as that describedin Embodiment 2. Specifically, a portion of a functional layer 36 thatis not supposed to contain a capturing substance 33 is formed, inadvance, on a hole-injecting electrode 12 by deposition. Subsequently, acapturing substance and a functional layer material are co-deposited ascontrolling the deposition rate so as to obtain a specified mixingratio. Thereby, a functional layer 36 can be formed in which thecapturing substance 33 is uniformly distributed on the side of anelectron-injecting electrode 35, within a given area. On the other hand,for formation of a functional layer 36 having a capturing substance 33distributed therein such that the concentration of the substancegradually increases toward the electron-injecting electrode 35, thelayer can be formed by increasing the deposition temperature(specifically, by increasing the amount of electric current).

Embodiment 5

[0223] Another embodiment of a thin film EL device according to thepresent invention is described below. It should be noted that thecomponents having the same functions as those of the thin film ELdevices of the foregoing embodiments are designated by the samereference numerals and thus will not be further described.

[0224] Thin film EL devices according to Embodiment 5 are different fromthin film EL devices according to each of the foregoing embodiments inthat both an electron-deficient substance and a capturing substance areutilized. A more detailed description is as follows.

[0225]FIG. 13 is a schematic cross-sectional view showing a thin film ELdevice according to Embodiment 5.

[0226] As shown in the figure, a thin film EL device 40 according to thepresent embodiment has at least a hole-injecting electrode 12, anelectron-injecting electrode 41 paired with the hole-injecting electrode12, and a functional layer 13 provided between the hole-injectingelectrode 12 and the electron-injecting electrode 41, stacked on top ofeach other on a substrate 11.

[0227] The electron-injecting electrode 41 is a multilayer electrodehaving an electron-deficient substance layer 16, a capture layer 32, anda metal layer 15, stacked in this order from the side of the functionallayer 13. The electron-deficient substance layer 16 has an excellentelectron transport property, and thus more electrons can be injectedinto the functional layer 13, whereby the recombination rate of holesand electrons is increased, improving electroluminescent efficiency. Inthe meantime, the capture layer 32 captures a low work function metalbefore the metal changes into an oxide or the like, thereby preventingdeterioration of the low work function metal. The provision of both theelectron-deficient substance layer 16 and the capture layer 32 withinone and the same device thus improves the light-emission lifetime andallows for light-emission with high luminance.

[0228] Furthermore, the electron-injecting electrode 41 may be amultilayer electrode having, in place of the metal layer 15, a low workfunction metal layer 22 and a passivating metal layer 18, stacked inthis order from the side of the capture layer 32.

[0229] Moreover, an electron-injecting electrode 41 may be a multilayerelectrode, as shown in FIG. 14, having an electron-deficient substancelayer 16, a low work function metal layer 22 containing a capturingsubstance 33, and a passivating metal layer 18, stacked in this orderfrom the side of a functional layer 13.

[0230] The electron-injecting electrode 41 may also be such that anelectron-deficient substance and a capturing substance are contained inthe same layer, and on this layer the metal layer 15 is stacked or thelow work function metal layer and the passivating metal layer arestacked on top of each other.

[0231] Since the electron-deficient substance has an excellent electrontransport property and the capturing substance is effective in capturinga low work function metal, it is advantageous that the capture layer 32be provided on the side of the metal layer 15 containing a low workfunction metal or on the side of the low work function metal layer 22.It should be noted, however, that there is possibility that thediffusion of the cations of the low work function metal into thefunctional layer 13 may deactivate the excited state of the luminescentmaterial in the functional layer 13. Thus, in order to prevent thedeactivation, the electron-injecting electrode 41 may be formed suchthat the capture layer 32/electron-deficient substance layer 16/metallayer 15 are stacked in this order from the side of the functional layer13. Alternatively, the electron-injecting electrode 41 may be formedsuch that the capture layer 32/electron-deficient substance layer 16/lowwork function metal layer 22/passivating metal layer 18 are stacked inthis order from the side of the functional layer 13.

Embodiment 6

[0232] Still another embodiment of a thin film EL device according tothe present invention is described below. It should be noted that thecomponents having the same functions as those of the thin film EL deviceof Embodiment 3 are designated by the same reference numerals and thuswill not be further described.

[0233] Thin film EL devices according to Embodiment 6 are different fromthin film EL devices according to Embodiment 3 in that anelectron-deficient substance and/or a capturing substance is(are)contained in the functional layer but not in the electron-injectingelectrode.

[0234] More specifically, for example, as shown in FIG. 15(a), it ispossible to employ a configuration in which an electron-injectingelectrode formed from a metal layer 15 is stacked on a functional layer51 having therein an electron-deficient substance 20 and a capturingsubstance 33 distributed on the side of the electron-injecting electrode31.

[0235] Furthermore, as shown in FIG. 15(b), in place of the metal layer15, a low work function metal layer 17 and a passivating metal layer 18can be stacked in this order from the side of a functional layer 51.

[0236] Moreover, it is also possible to employ a configuration in whichone of the electron-deficient substance 20 and the capturing substance33 is contained in the functional layer and the other is contained inthe electron-injecting electrode.

[0237] (Miscellaneous)

[0238] It should be noted that each of the foregoing embodimentsdescribed the configuration in which the hole-injecting electrode, thefunctional layer, and the electron-injecting electrode are sequentiallyprovided on the substrate, but the present invention is not limitedthereto. For example, a device may be such that the electron-injectingelectrode, the functional layer, and the hole-injecting electrode aresequentially stacked on the substrate.

[0239] Furthermore, each of the foregoing embodiments described, as anexample, a thin film EL device that provides planar light emission fromthe substrate side, but light can also be extracted from theelectron-injecting electrode side. In the present invention, asdescribed in, for example, Embodiments 1, 3, and 5, theelectron-deficient substance layer and/or the capture layer, forexample, is(are) provided on the functional layer, and therefore damageto the functional layer can be minimized during the formation of the lowwork function metal layer and the like. Minimization of damage to thefunctional layer allows for the formation of a transparent ortranslucent conductive film, instead of a passivating metal layercomposed of Al or the like. Examples of the transparent or translucentconductive film include alloy thin films and the like composed of ITO,Au, an Mg—Ag alloy, an Ag—Pd—Cu alloy, or the like. Consequently, thefollowing additional effects were achieved. Namely, when light isobtained through a transparent substrate such as a glass substrate, allthe light emitted from the functional layer does not pass through thesubstrate; part of the light is lost by total reflection within thesubstrate. However, with the above-described configuration, light can beextracted without allowing it to pass through the substrate, andtherefore the loss of light can be minimized and the light extractionefficiency can be significantly improved. In this case, the visiblelight transmittance of the electron-injecting electrode is preferably50% or more, and more preferably 70% or more.

[0240] It should be noted that each of the foregoing embodimentsdescribed, as an example, a direct-current drive thin film EL device,but the present invention is not limited thereto. For example, it isalso possible to employ an alternating current drive type or a pulsedrive type.

[0241] Furthermore, an electrode having an electron-deficient substanceand/or a capturing substance according to the present invention can beapplied to bio sensors and photoelectric converters (for example, solarbatteries and optical sensors) in addition to thin film EL devices.

[0242] Now, the present invention is described in more detail withreference to the examples and comparative examples but is not limitedthereto. It should be noted that the following Examples 1 to 3 relate tothin film EL devices utilizing electron-deficient substances, thefollowing Examples 4 to 7 to thin film EL devices utilizing capturingsubstances, and Examples 8 to 10 to thin film EL devices utilizingelectron-deficient substances and capturing substances.

EXAMPLE 1

[0243] First, an ITO (Indium Tin Oxide) film (hole-injecting electrode)was formed on a glass substrate by sputtering. Next, usingN,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine as ahole-transport layer material, a hole-transport layer was formed on theITO film by deposition. The film thickness of the hole-transport layerwas 50 nm.

[0244] Subsequently, using tris(8-quinolinolato)aluminum as an organicluminescent layer material, an organic luminescent layer (luminescentlayer) was formed on the hole-transport layer by deposition. The filmthickness of the organic luminescent layer was 50 nm. In addition, using4,4,8,8-tetraphenylpyrazabole as an electron-deficient substance, anelectron-deficient substance layer was formed on the organic luminescentlayer by deposition. The film thickness of the electron-deficientsubstance layer was 1 nm.

[0245] Then, an Li film (low work function metal layer) of 0.5 nmthickness was formed on the electron-deficient substance layer bydeposition. Further, on the Li film, an Al film (passivating metallayer) of 100 nm thickness was formed. Thereby, a thin film EL device ofthe present invention was fabricated.

[0246] The electroluminescent characteristics were measured byconnecting the power supply to the ITO film and Al film of the thin filmEL device and applying a direct-current voltage thereto. As a result,with an applied voltage of about 4 V, a luminance (luminescence level)of about 500 cd/m² and an electroluminescent efficiency of 5.0 cd/A wereobtained.

[0247] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 700 hoursat an initial luminance of 300 cd/m². These results are shown in Table 1below.

[0248] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

EXAMPLE 2

[0249] A thin film EL device according to Example 2 is different from athin film EL device according to Example 1 in that instead of providingthe electron-deficient substance layer, a luminescent layer containingan electron-deficient substance is provided.

[0250] An organic luminescent layer according to Example 2 was formed inthe following manner. Specifically, using tris(8-quinolinolato)aluminumas an organic luminescent layer material, a single layer composed of anorganic luminescent material (film thickness of 40 nm) was formed on ahole-transport layer by deposition. Subsequently, tris(8-quinolinolato)aluminum and 4,4,8,8-tetraphenylpyrazabole as an electron-deficientsubstance were co-deposited, thus forming a layer (film thickness of 10nm) in which the electron-deficient substance was uniformly distributedin the organic luminescent material. Thereby, an organic luminescentlayer (luminescent layer, film thickness of 50 nm) was formed. It shouldbe noted that the weight ratio of the organic luminescent layer materialto the electron-deficient substance material was made to be 9:1.

[0251] The thin film EL device according to Example 2 was examined forits electroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 4 V, a luminance(luminescence level) of about 500 cd/m² and an electroluminescentefficiency of 5.0 cd/A were obtained.

[0252] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 700 hoursat an initial luminance of 300 cd/M². These results are shown in Table 1below.

[0253] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

EXAMPLE 3

[0254] A thin film EL device according to Example 3 is different from athin film EL device according to Example 1 in that an electron-deficientsubstance is contained in the Li layer.

[0255] An electron-deficient substance layer according to Example 3 wasformed, by co-deposition, on an organic luminescent layer such that themol ratio of Li to an electron-deficient substance is 1:1.

[0256] The thin film EL device according to Example 2 was examined forits electroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 4 V, a luminance(luminescence level) of about 500 cd/M² and an electroluminescentefficiency of 5.0 cd/A were obtained.

[0257] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 700 hoursat an initial luminance of 300 cd/m². These results are shown in Table 1below.

[0258] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

EXAMPLE 4

[0259] A thin film EL device according to Example 4 is different from athin film EL device according to Example 1 in that a capture layer isprovided in place of the electron-deficient substance layer.

[0260] A capture layer according to Example 4 was formed, by deposition,on the organic luminescent layer, using, as a capturing substance,4,4,8,8-tetrakis(1H-pyrazole-1-yl)pyrazabole having anelectron-accepting property. The film thickness of the capture layer was1 nm.

[0261] The thin film EL device according to Example 4 was examined forits electroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 4 V, a luminance(luminescence level) of about 500 cd/m² and an electroluminescentefficiency of 6.0 cd/A were obtained.

[0262] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 700 hoursat an initial luminance of 300 cd/m². These results are shown in Table 1below.

[0263] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

EXAMPLE 5

[0264] A thin film EL device according to Example 5 is different from athin film EL device according to Example 4 in that the film thickness ofa capture layer is 2 nm but not 1 nm.

[0265] The thin film EL device according to Example 4 was examined forits electroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 4 V, a luminance(luminescence level) of about 600 cd/m² and an electroluminescentefficiency of 6.0 cd/A were obtained.

[0266] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 1000hours at an initial luminance of 300 cd/m². These results are shown inTable 1 below.

[0267] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

EXAMPLE 6

[0268] A thin film EL device according to Example 6 is different from athin film EL device according to Example 5 in that instead of providingthe capture layer, an organic luminescent layer containing a capturingsubstance is provided.

[0269] An organic luminescent layer according to Example 6 was formed inthe following manner. Specifically, using tris(8-quinolinolato)aluminumas an organic luminescent layer material, a single layer composed of anorganic luminescent material (film thickness of 40 nm) was formed on ahole-transport layer by deposition. Subsequently, tris(8-quinolinolato)aluminum and 4,4,8,8-tetrakis(1H-pyrazole-1-yl)pyrazabole as a capturingsubstance were co-deposited, thus forming a layer (film thickness of 10nm) in which the capturing substance was uniformly distributed in theorganic luminescent material. Thereby, an organic luminescent layerLuminescent layer, film thickness of 50 nm) was formed. It should benoted that the weight ratio of the organic luminescent layer material tothe capturing substance material was made to be 8:2.

[0270] The thin film EL device according to Example 6 was examined forits electroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 4 V, a luminance(luminescence level) of about 600 cd/m² and an electroluminescentefficiency of 6.0 cd/A were obtained.

[0271] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 1000hours at an initial luminance of 300 cd/M². These results are shown inTable 1 below.

[0272] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

EXAMPLE 7

[0273] A thin film EL device according to Example 7 is different from athin film EL device according to Example 5 in that a capturing substanceis contained in the Li layer.

[0274] An electron-deficient substance layer according to Example 3 wasformed, by co-deposition, on an organic luminescent layer such that themol ratio of Li to a capturing substance is 1:2.

[0275] The thin film EL device according to Example 2 was examined forits electroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 4 V, a luminance(luminescence level) of about 600 cd/m² and an electroluminescentefficiency of 6.0 cd/A were obtained.

[0276] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 1000hours at an initial luminance of 300 cd/m². These results are shown inTable 1 below.

[0277] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

EXAMPLE 8

[0278] A thin film EL device according to Example 8 is different from athin film EL device according to Example 1 in that a capture layer isprovided on the electron-deficient substance layer. More specifically,an electron-deficient substance layer of 10 nm film thickness and acapture layer of 5 nm film thickness are sequentially provided on anorganic luminescent layer of 30 nm film thickness. In addition, inExample 8, as the anode, an ITO film of 100 nm film thickness was formedin place of the Al film.

[0279] The thin film EL device according to Example 8 was examined forits electroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 5 V, a luminance(luminescence level) of about 500 cd/m² and an electroluminescentefficiency of 5.5 cd/A were obtained.

[0280] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 1800hours at an initial luminance of 300 cd/m². These results are shown inTable 1 below.

[0281] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

EXAMPLE 9

[0282] A thin film EL device according to Example 9 is different from athin film EL device according to Example 8 in that an organicluminescent layer (film thickness of 20 nm) containing anelectron-deficient substance is provided in place of theelectron-deficient substance layer.

[0283] An organic luminescent layer according to Example 9 was formed inthe following manner. Specifically, using tris(8-quinolinolato)aluminumas an organic luminescent layer material, a single layer (film thicknessof 20 nm) composed of an organic luminescent material was formed on ahole-transport layer by deposition. Subsequently, tris(8-quinolinolato)aluminum and 4,4,8,8-tetraphenylpyrazabole as an electron-deficientsubstance were co-deposited, thus forming a layer (film thickness of 20nm) in which the electron-deficient substance was uniformly distributedin the organic luminescent material. Thereby, an organic luminescentlayer (luminescent layer, film thickness of 40 nm) was formed. It shouldbe noted that the weight ratio of the organic luminescent layer materialto the electron-deficient substance material was made to be 1:1.

[0284] The thin film EL device according to Example 9 was examined forits electroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 5 V, a luminance(luminescence level) of about 500 cd/m² and an electroluminescentefficiency of 5.5 cd/A were obtained.

[0285] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 1800hours at an initial luminance of 300 cd/m². These results are shown inTable 1 below.

[0286] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

EXAMPLE 10

[0287] A thin film EL device according to Example 10 is different from athin film EL device according to Example 8 in that a capturing substanceis contained in the Li layer.

[0288] A capture layer according to Example 10 was formed, byco-deposition, on an electron-deficient substance layer such that themol ratio of a capturing substance material to Li is 1:2.

[0289] The thin film EL device according to Example 10 was examined forits electroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 5 V, a luminance(luminescence level) of about 500 cd/m² and an electroluminescentefficiency of 5.5 cd/A were obtained.

[0290] Furthermore, a continuous light-emission test at constant currentwas conducted on the thin film EL device according to the presentexample. As a result, the lifetime to half luminance was about 1800hours at an initial luminance of 300 cd/m². These results are shown inTable 1 below.

[0291] Moreover, a display device was fabricated in which theabove-described thin film EL devices were arranged in a 100×100 matrix.The display device was allowed to display moving images, and it wasconfirmed that good quality images can be obtained with this device.

Comparative Example 1

[0292] A thin film EL device for comparison according to ComparativeExample 1 is different from a thin film EL device according to Example 1in that the device does not have the electron-deficient substance layer.

[0293] The thin film EL device for comparison was measured for itselectroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 5 V, a luminance of about300 cd/M² and an electroluminescent efficiency of 3.5 cd/A wereobtained.

[0294] Furthermore, a continuous light-emission test at constant currentwas conducted. The lifetime to half luminance was about 100 hours at aninitial luminance of 300 cd/M². These results are shown in Table 1below.

[0295] Comparative Example 2

[0296] A thin film EL device for comparison according to ComparativeExample 1 is different from a thin film EL device according to Example 1in that the device does not have the Li film.

[0297] The thin film EL device for comparison was measured for itselectroluminescent characteristics in the same manner as that ofExample 1. With an applied voltage of about 4 V, a luminance of about500 cd/m² and an electroluminescent efficiency of 4.5 cd/A wereobtained.

[0298] Furthermore, a continuous light-emission test at constant currentwas conducted. The lifetime to half luminance was about 550 hours at aninitial luminance of 300 cd/M². These results are shown in Table 1below.

[0299] (Results)

[0300] As is clear from Table 1 below, it was found that thin film ELdevices according to the present invention which includedelectron-deficient substances and/or capturing substances had higherelectroluminescent efficiencies and excellent electroluminescentcharacteristics as compared with thin film EL devices for comparison. Inaddition, the lifetimes to half luminance for initial luminance arelong, as a result of which it was confirmed that a decrease in lifetimewas inhibited. TABLE 1 Electro- Initial Lifetime Applied luminescentlumin- to half voltage Luminance efficiency ance luminance (V) (cd/m²)(cd/A) (cd/m²) (hr) Example 1 4 500 5.0 300  700 Example 2 4 500 5.0 300 700 Example 3 4 500 5.0 300  700 Example 4 4 500 6.0 300  700 Example 54 600 6.0 300 1000 Example 6 4 600 6.0 300 1000 Example 7 4 600 6.0 3001000 Example 8 5 500 5.5 300 1800 Example 9 5 500 5.5 300 1800 Example10 5 500 5.5 300 1800 Comparatave 5 300 3.5 300  100 Example 1Comparative 4 500 4.5 300  550 Example 2

[0301] The specific embodiments or examples given in the detaileddescription of the preferred embodiments are intended solely forpurposes of illustration of principles of the invention and are not tobe construed as limiting the invention. Accordingly, variousmodifications can be made to the described embodiments or exampleswithout departing from the spirit and scope of the invention as setforth in the claims below.

INDUSTRIAL APPLICABILITY

[0302] As has been described, thin film EL devices according to thepresent invention are capable of capturing cations of a low workfunction metal, and thus the deterioration of the low work functionmetal can be inhibited. This allows improvement in theelectroluminescent efficiency of the device and dramatic improvement inlifetime characteristics.

[0303] Furthermore, with the fabrication methods of thin film EL devicesaccording to the present invention, thin film EL devices with highelectroluminescent efficiencies and long light-emission lifetimes can befabricated with good workability, good reproducibility, and improvedyields, while inhibiting deterioration of the low work function metaloccurring even during the fabrication process.

[0304] In display devices provided with thin film EL devices accordingto the present invention, because the devices include thin film ELdevices with high electroluminescent efficiencies, high reliability, andlong lifetimes, high-grade display devices can be provided.

[0305] Lighting systems provided with thin film EL devices according tothe present invention have electroluminescent characteristics such ashigh electroluminescent efficiencies, high reliability, and longlifetimes, and thus high-grade lighting systems can be provided whichare applicable, for example, to backlights for liquid crystal displays.

[0306] As has been discussed, according to the configurations of thepresent invention, the objects of the present invention can besufficiently accomplished. Thus, the value of the present invention toindustry is considerable.

What is claimed is:
 1. (Amended) An electrode comprising: at least twoor more different metals having different work functions; and anelectron-deficient substance for accepting electrons emitted from a lowwork function metal, the low work function metal being a metal otherthan a highest work function metal among the metals, wherein theelectron-deficient substance is an organic metal compound or aninorganic metal compound, the organic metal compound being composed of adinuclear complex containing a metal or semimetal atom as a centralatom.
 9. (Amended) An electrode comprising: at least two or moredifferent metals having different work functions; and a capturingsubstance for capturing a low work function metal in its ionic state andcontaining an atom selected from the group consisting of Li, Be, B, Mg,Al, Ca, Zn, and Ga, the low work function metal being a metal other thana highest work function metal among the metals.
 39. (Amended) A thinfilm EL device comprising: an electron-injecting electrode containing atleast two or more different metals having different work functions; ahole-injecting electrode paired with the electron-injecting electrode;and a functional layer provided between the electron-injecting electrodeand the hole-injecting electrode and having a light-emitting function,wherein the electron-injecting electrode contains an electron-deficientsubstance for accepting electrons emitted from a low work functionmetal, the electron-deficient substance containing an organic metalcompound or an inorganic metal compound, the organic metal compoundbeing composed of a dinuclear complex containing a metal or semimetalatom as a central atom, the low work function metal being a metal otherthan a highest work function metal among the metals.
 65. (Amended) Athin film EL device comprising: an electron-injecting electrodecontaining at least two or more different metals having different workfunctions; a hole-injecting electrode paired with the electron-injectingelectrode; and a functional layer provided between theelectron-injecting electrode and the hole-injecting electrode and havinga light-emitting function, wherein the electron-injecting electrodecontains a capturing substance for capturing a low work function metalin its ionic state, the capturing substance containing an atom selectedfrom the group consisting of Li, Be, B, Mg, Al, Ca, Zn, and Ga and thelow work function metal being a metal other than a highest work functionmetal among the metals.
 76. (Amended) A thin film EL device comprising:an electron-injecting electrode containing at least two or moredifferent metals having different work functions; a hole-injectingelectrode paired with the electron-injecting electrode; and a functionallayer provided between the electron-injecting electrode and thehole-injecting electrode and having a light-emitting function, whereinthe functional layer contains on a side of the electron-injectingelectrode a capturing substance for capturing a low work function metalin its ionic state, the low work function metal being a metal other thana highest work function metal among the metals.
 85. (Amended) A thinfilm EL device comprising: an electron-injecting electrode; ahole-injecting electrode paired with the electron-injecting electrode;and a functional layer provided between the electron-injecting electrodeand the hole-injecting electrode and having a light-emitting function,wherein the functional layer contains a low work function metal and acapturing substance for capturing the low work function metal in itsionic state, the low work function metal having a lower work functionthan the electron-injecting electrode.
 95. (Amended) A thin film ELdevice comprising: an electron-injecting electrode containing at leasttwo or more different metals having different work functions; ahole-injecting electrode paired with the electron-injecting electrode;and a functional layer provided between the electron-injecting electrodeand the hole-injecting electrode and having a light-emitting function,wherein the electron-injecting electrode contains: an electron-deficientsubstance for accepting electrons emitted from a low work functionmetal, the low work function metal being a metal other than a highestwork function metal among the metals; and a capturing substance forcapturing the low work function metal in its ionic state.
 105. (Amended)A thin film EL device comprising: an electron-injecting electrodecontaining at least two or more different metals having different workfunctions; a hole-injecting electrode paired with the electron-injectingelectrode; and a functional layer provided between theelectron-injecting electrode and the hole-injecting electrode and havinga light-emitting function, wherein the functional layer contains anelectron-deficient substance for accepting electrons emitted from a lowwork function metal and a capturing substance for capturing the low workfunction metal in its ionic state, the low work function metal being ametal other than a highest work function metal among the metals. 115.(Amended) A thin film EL device comprising: an electron-injectingelectrode; a hole-injecting electrode paired with the electron-injectingelectrode; and a functional layer provided between theelectron-injecting electrode and the hole-injecting electrode and havinga light-emitting function, wherein the functional layer contains a lowwork function metal having a lower work function than theelectron-injecting electrode, a capturing substance for capturing thelow work function metal in its ionic state, and an electron-deficientsubstance for accepting electrons emitted from the low work functionmetal.
 125. (Amended) A thin film EL device comprising: anelectron-injecting electrode containing at least two or more differentmetals having different work functions; a hole-injecting electrodepaired with the electron-injecting electrode; and a functional layerprovided between the electron-injecting electrode and the hole-injectingelectrode and having a light-emitting function, wherein one of anelectron-deficient substance for accepting electrons emitted from a lowwork function metal and a capturing substance for capturing the low workfunction metal in its ionic state is contained in the electron-injectingelectrode and the other is contained in the functional layer, the lowwork function metal being a metal other than a highest work functionmetal among the metals.
 133. (Amended) A method of fabricating a thinfilm EL device having an electron-injecting electrode containing atleast two or more different metals having different work functions, ahole-injecting electrode, and a functional layer provided between theelectrodes and having a light-emitting function, the method comprising:forming the electron-injecting electrode, the forming of theelectron-injecting electrode comprising at least: forming on a side ofthe functional layer an electron-deficient substance layer containing anelectron-deficient substance for accepting electrons emitted from a lowwork function metal, the electron-deficient substance containing anorganic metal compound or an inorganic metal compound, the organic metalcompound being composed of a dinuclear complex containing a metal orsemimetal atom as a central atom, the low work function metal being ametal other than a highest work function metal among the metals; andforming on an opposite side from the functional layer a metal layercontaining the two or more different metals.
 134. (Amended) A method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole injecting electrode, and a functional layer providedbetween the electrodes and having a light-emitting function, the methodcomprising: forming the electron-injecting electrode, the forming of theelectron-injecting electrode comprising at least: forming on a side ofthe functional layer an electron-deficient substance layer containing alow work function metal and an electron-deficient substance foraccepting electrons emitted from the low work function metal, the lowwork function metal being a metal other than a highest work functionmetal among the metals.
 135. (Amended) A method of fabricating a thinfilm EL device having an electron-injecting electrode containing atleast two or more different metals having different work functions, ahole-injecting electrode, and a functional layer provided between theelectrodes and having a light-emitting function, the method comprising:forming the functional layer so that an electron-deficient substance isdistributed in the functional layer at least on a side of theelectron-injecting electrode, the electron-deficient substance acceptingelectrons emitted from a low work function metal, the low work functionmeal being a metal other than a highest work function metal among themetals.
 136. (Amended) A method of fabricating a thin film EL devicehaving an electron-injecting electrode, a hole-injecting electrode, anda functional layer provided between the electrodes and having alight-emitting function, the method comprising: forming the functionallayer so that a low work function metal and an electron-deficientsubstance are distributed in the functional layer at least on a side ofthe electron-injecting electrode, the low work function metal being ametal other than a highest work function metal among the metals and theelectron-deficient substance accepting electrons emitted from the lowwork function metal.
 137. (Amended) A method of fabricating a thin filmEL device having an electron-injecting electrode containing at least twoor more different metals having different work functions, ahole-injecting electrode, and a functional layer provided between theelectrodes and having a light-emitting function, the method comprising:forming the electron-injecting electrode, the forming of theelectron-injecting electrode comprising at least: forming on a side ofthe functional layer a capture layer containing a capturing substancefor capturing a low work function metal in its ionic state, thecapturing substance containing an atom selected from the groupconsisting of Li, Be, B, Mg, Al, and Zn and the low work function metalbeing a metal other than a highest work function metal among the metals;and forming a metal layer on an opposite side from the functional layer,the metal layer containing an alloy composed of the two or moredifferent metals.
 138. (Amended) A method of fabricating a thin film ELdevice having an electron-injecting electrode containing at least two ormore different metals having different work functions, a hole-injectingelectrode, and a functional layer provided between the electrodes andhaving a light-emitting function, the method comprising: forming theelectron-injecting electrode, the forming of the electron-injectingelectrode comprising at least: forming on a side of the functional layera capture layer containing a low work function metal and a capturingsubstance, the low work function metal being a metal other than ahighest work function metal among the metals and the capturing substancecapturing the low work function metal in its ionic state.
 139. (Amended)A method of fabricating a thin film EL device having anelectron-injecting electrode containing at least two or more differentmetals having different work functions, a hole-injecting electrode, anda functional layer provided between the electrodes and having alight-emitting function, the method comprising: forming the functionallayer so that a capturing substance is distributed in the functionallayer at least on a side of the electron-injecting electrode, thecapturing substance capturing a low work function metal in its ionicstate, the low work function metal being a metal other than a highestwork function metal among the metals.
 140. (Amended) A method offabricating a thin film EL device having an electron-injectingelectrode, a hole-injecting electrode, and a functional layer providedbetween the electrodes and having a light-emitting function, the methodcomprising: forming the functional layer so that a low work functionmetal and a capturing substance are distributed in the functional layerat least on a side of the electron-injecting electrode, the low workfunction metal being a metal other than a highest work function metalamong the metals and the capturing substance capturing the low workfunction metal in its ionic state.
 141. (Amended) A method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole-injecting electrode, and a functional layer providedbetween the electrodes and having a light-emitting function, the methodcomprising: forming the electron-injecting electrode, the forming of theelectron-injecting electrode comprising at least: forming anelectron-deficient substance layer containing an electron-deficientsubstance for accepting electrons emitted from a low work functionmetal, the low work function metal being a metal other than a highestwork function metal among the metals; forming a capture layer containinga capturing substance for capturing the low work function metal in itsionic state; and forming a metal layer on the electron-deficientsubstance layer or the capture layer, the metal layer containing the twoor more different metals.
 142. (Amended) A method of fabricating a thinfilm EL device having an electron-injecting electrode containing atleast two or more different metals having different work functions, ahole-injecting electrode, and a functional layer provided between theelectrodes and having a light-emitting function, the method comprising:forming the electron-injecting electrode, the forming of theelectron-injecting electrode comprising at least: forming a layercontaining a low work function metal, an electron-deficient substance,and a capturing substance, the low work function metal being a metalother than a highest work function metal among the metals, theelectron-deficient substance accepting electrons emitted from the lowwork function metal, and the capturing substance capturing the low workfunction metal in its ionic state.
 143. (Amended) A method offabricating a thin film EL device having an electron-injecting electrodecontaining at least two or more different metals having different workfunctions, a hole-injecting electrode, and a functional layer providedbetween the electrodes and having a light-emitting function, the methodcomprising: forming the electron-injecting electrode, the forming of theelectron-injecting electrode comprising at least: forming anelectron-deficient substance layer containing an electron-deficientsubstance for accepting electrons emitted from a low work functionmetal, the low work function metal being a metal other than a highestwork function metal among the metals; and forming a capture layercontaining the low work function metal and a capturing substance forcapturing the low work function metal in its ionic state.
 144. (Amended)A method of fabricating a thin film EL device having anelectron-injecting electrode containing at least two or more differentmetals having different work functions, a hole-injecting electrode, anda functional layer provided between the electrodes and having alight-emitting function, the method comprising: forming the functionallayer so that an electron-deficient substance for accepting electronsemitted from a low work function metal and a capturing substance forcapturing the low work function metal in its ionic state are distributedin the functional layer at least on a side of the electron-injectingelectrode, the low work function metal being a metal other than ahighest work function metal among the metals.
 145. (Amended) A method offabricating a thin film EL device having an electron-injectingelectrode, a hole-injecting electrode, and a functional layer providedbetween the electrodes and having a light-emitting function, the methodcomprising: forming the functional layer so that a low work functionmetal, an electron-deficient substance, and a capturing substance aredistributed in the functional layer at least on a side of theelectron-injecting electrode, the low work function metal being a metalother than a highest work function metal among the metals, theelectron-deficient substance accepting electrons emitted from the lowwork function metal, and the capturing substance capturing the low workfunction metal in its ionic state.
 146. (Amended) A display devicecomprising: an electron-injecting electrode containing at least two ormore different metals having different work functions; a hole-injectingelectrode paired with the electron-injecting electrode; and a functionallayer provided between the electron-injecting electrode and thehole-injecting electrode and having a light-emitting function, whereinthe electron-injecting electrode contains an electron-deficientsubstance for accepting electrons emitted fiom a low work functionmetal, the low work function metal being a metal other than a highestwork function metal among the metals.
 147. (Amended) A display devicecomprising: a hole-injecting electrode; an electron-injecting electrodepaired with the hole-injecting electrode; and a functional layerprovided between the hole-injecting electrode and the electron-injectingelectrode and having a light-emitting function, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains an electron-deficient substance for accepting electrons emittedfrom the low work function metal.
 148. (Amended) A display devicecomprising: an electron-injecting electrode containing at least two ormore different metals having different work functions; a hole-injectingelectrode paired with the electron-injecting electrode; a functionallayer provided between the electron-injecting electrode and thehole-injecting electrode and having a light-emitting function, whereinthe electron-injecting electrode contains a capturing substance forcapturing a low work function metal in its ionic state, the low workfunction metal being a metal other than a highest work function metalamong the metals.
 149. (Amended) A display device comprising: ahole-injecting electrode; an electron-injecting electrode paired withthe hole-injecting electrode; a functional layer provided between thehole-injecting electrode and the electron-injecting electrode and havinga light-emitting function, wherein one of the electron-injectingelectrode and the functional layer contains a low work function metalhaving a lower work function than a metal composing theelectron-injecting electrode, and wherein the functional layer containsa capturing substance for capturing the low work function metal in itsionic state.
 150. (Amended) A display device comprising: anelectron-injecting electrode containing at least two or more differentmetals having different work functions; a hole-injecting electrodepaired with the electron-injecting electrode; and a functional layerprovided between the electron-injecting electrode and the hole-injectingelectrode and having a light-emitting function, wherein theelectron-injecting electrode contains: an electron-deficient substancefor accepting electrons emitted from a low work function metal, the lowwork function metal being a metal other than a highest work functionmetal among the metals; and a capturing substance for capturing the lowwork function metal in its ionic state.
 151. (Amended) A display devicecomprising: a hole-injecting electrode; an electron-injecting electrodepaired with the hole-injecting electrode; and a functional layerprovided between the hole-injecting electrode and the electron-injectingelectrode and having a light-emitting function, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains an electron-deficient substance for accepting electrons emittedfrom a low work function metal and a capturing substance for capturingthe low work function metal in its ionic state, the low work functionmetal being a metal other than a highest work function metal among themetals.
 152. (Amended) A display device comprising: anelectron-injecting electrode containing at least two or more differentmetals having different work functions; a hole-injecting electrodepaired with the electron-injecting electrode; and a functional layerprovided between the electron-injecting electrode and the hole-injectingelectrode and having a light-emitting function, wherein one of acapturing substance for capturing a low work function metal in its ionicstate and an electron-deficient substance for accepting electronsemitted from the low work function metal is contained in theelectron-injecting electrode and the other is contained in thefunctional layer, the low work function metal being a metal other than ahighest work function metal among the metals.
 153. (Amended) Alightingsystem comprising: an electron-injecting electrode containing at leasttwo or more different metals having different work functions; ahole-injecting electrode paired with the electron-injecting electrode; afunctional layer provided between the electron-injecting electrode andthe hole-injecting electrode and having a light-emitting function,wherein the electron-injecting electrode contains an electron-deficientsubstance for accepting electrons emitted fiom a low work functionmetal, the low work function metal being a metal other than a highestwork function metal among the metals.
 154. (Amended) A lighting systemcomprising: a hole-injecting electrode; an electron-injecting electrodepaired with the hole-injecting electrode; and a functional layerprovided between the hole-injecting electrode and the electron-injectingelectrode and having a light-emitting function, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains an electron-deficient substance for accepting electrons emittedfrom the low work function metal.
 155. (Amended) Alighting systemcomprising: an electron-injecting electrode containing at least two ormore different metals having different work functions; a hole-injectingelectrode paired with the electron-injecting electrode; a functionallayer provided between the electron-injecting electrode and thehole-injecting electrode and having a light-emitting function, whereinthe electron-injecting electrode contains a capturing substance forcapturing a low work function metal in its ionic state, the low workfunction metal being a metal other than a highest work function metalamong the metals.
 156. (Amended) A lighting system comprising: ahole-injecting electrode; an electron-injecting electrode paired withthe hole-injecting electrode; and a functional layer provided betweenthe hole-injecting electrode and the electron-injecting electrode andhaving a light-emitting function, wherein one of the electron-injectingelectrode and the functional layer contains a low work function metalhaving a lower work function than a metal composing theelectron-injecting electrode, and wherein the functional layer containsa capturing substance for capturing the low work function metal in itsionic state.
 157. (Amended) A lighting system comprising: anelectron-injecting electrode containing at least two or more differentmetals having different work functions; a hole-injecting electrodepaired with the electron-injecting electrode; and a functional layerprovided between the electron-injecting electrode and the hole-injectingelectrode and having a light-emitting function, wherein theelectron-injecting electrode contains: an electron-deficient substancefor accepting electrons emitted from a low work function metal, the lowwork function metal being a metal other than a highest work functionmetal among the metals; and a capturing substance for capturing the lowwork function metal in its ionic state.
 158. (Amended) A lighting systemcomprising: a hole-injecting electrode; an electron-injecting electrodepaired with the hole-injecting electrode; and a functional layerprovided between the hole-injecting electrode and the electron-injectingelectrode and having a light-emitting function, wherein one of theelectron-injecting electrode and the functional layer contains a lowwork function metal having a lower work function than a metal composingthe electron-injecting electrode, and wherein the functional layercontains an electron-deficient substance for accepting electrons emittedfrom a low work function metal and a capturing substance for capturingthe low work function metal in its ionic state, the low work functionmetal being a metal other than a highest work function metal among themetals.
 159. (Amended) A lighting system comprising: anelectron-injecting electrode containing at least two or more differentmetals having different work functions; a hole-injecting electrodepaired with the electron-injecting electrode; a functional layerprovided between the electron-injecting electrode and the hole-injectingelectrode and having a light-emitting function, wherein one of acapturing substance for capturing a low work function metal in its ionicstate and an electron-deficient substance for accepting electronsemitted from the low work function metal is contained in theelectron-injecting electrode and the other is contained in thefunctional layer, the low work function metal being a metal other than ahighest work function metal among the metals.